JP3663289B2 - Magnetic recording medium and magnetic storage device - Google Patents

Description

【００７８】
表１に示したＢｒｔ、Ｓ＊、Ｓ、ｖＩｓは、それぞれ残留磁化と情報記録層の膜厚の積、保磁力角形比、角形比、活性化磁気モーメントを示している。活性化磁気モーメントｖＩｓの測定方法は、例えば、ジャーナル オブ マグネティズム アンド マグネティック マテリアルズ、第１５２巻（１９９６）４１１〜４１６頁（Ｊｏｕｒｎａｌ ｏｆ Ｍａｇｎｅｔｉｓｍ ａｎｄ Ｍａｇｎｅｔｉｃ Ｍａｔｅｒｉａｌｓ，ｖｏｌ．１５２（１９９６）ｐｐ．４１１〜４１６）又は信学技報（ＴＥＣＨＮＩＣＡＬ ＲＥＰＯＲＴ ＯＦ ＩＥＩＣＥ）ＭＲ９６−４（１９９６−０６）に記載されている方法を用いた。このｖＩｓと高線記録密度におけるノイズの関係を調べた結果、定性的にｖＩｓの減少と共に媒体ノイズは低下しており、両者に強い相関があることが分かった。
【００７９】
高線記録密度（２Ｆ）における出力と媒体ノイズの割合Ｓ／Ｎｄを次式で定義した。
Ｓ／Ｎｄ＝２０ ｌｏｇ［Ｅ（２Ｆ）ｐｐ／２Ｎｄ］
１７２ｋＦＣＩと１８０ｋＦＣＩで測定したＳ／Ｎｄと出力分解能の関係は、いずれの線記録密度でも、実施例１に示した磁気記録媒体が比較例１、２のそれよりもＳ／Ｎｄと出力分解能が高かった。
【００８０】
１７２ｋＦＣＩにおけるノイズとｖＩｓの関係で、実施例１に示した磁気記録媒体のＮｄに比べ、比較例１に示した磁気記録媒体のＮｄは低かったが、１７２ｋＦＣＩにおける出力は実施例１の方が比較例１に比べ大きかったために、Ｓ／Ｎｄは実施例１に示した磁気記録媒体が最も高かった。
これらの結果を図２ａから図７ｂに示す。
【００８１】
〈実施例２〉
これらの磁気記録媒体について、同一ヘッドを用いて周波数を変化させ、２００ｋＦＣＩにおける電磁変換特性を評価した。その結果、２００ｋＦＣＩにおける出力分解能は１８０ｋＦＣＩにおける値に比べ小さくなるものの、実施例１に示した磁気記録媒体の出力分解能Ｒｅ及びＳＬＦ／Ｎｄ、Ｓ／Ｎｄが比較例に記載した磁気記録媒体に比べ大きかった。
【００８２】
〈実施例３〉
また、これらの磁気記録媒体について、同一ヘッドを用いて磁気記録媒体の回転数を変化させることによりヘッドの浮上量ｈｍを変化させ、１７２ｋＦＣＩにおける電磁変換特性を評価した。その結果、ｈｍ＝５６ｎｍ、６５ｎｍ、８１ｎｍの場合でも、実施例１に示した磁気記録媒体の出力分解能Ｒｅ及びＳＬＦ／Ｎｄ、Ｓ／Ｎｄが比較例に記載した磁気記録媒体に比べ大きかった。
【００８３】
〈実施例４〉
放電ガス圧力を２０ｍＴｏｒｒに一定にして、Ａｒ中に含有する窒素濃度を３％又は５％とした他は実施例１の記載と同様にして磁気記録媒体を形成し、これらの磁気記録媒体のｖＩｓを測定した。その結果を図８に示す。窒素を無添加で非磁性中間層を形成した比較例２の場合に比べ、窒素添加濃度を３〜５％とした場合には、ｖＩｓ値は小さくなった。さらに、窒素添加濃度を１０％にした場合には、窒素添加濃度を３〜５％とした場合に比べ更にｖＩｓ値は小さくなった。このように窒素を添加して形成した媒体のｖＩｓ値は小さくなる。なお、窒素添加濃度が３％、１０％では、非磁性中間層中にそれぞれ約１９原子％、約３１原子％の窒素がＣｒに対して含まれる。
【００８４】
また、非磁性中間層の膜厚を１０ｎｍから１００ｎｍまで変化させた試作円板でも、上記と同様の傾向を有する優れた記録再生特性が得られた。
【００８５】
〈実施例５〉
実施例１と同様に窒素を添加したＡｒガス中で、放電ガス圧力２０ｍＴｏｒｒでスパッタすることにより、優位的に酸化したＺｒと窒素を同時に含有したＣｒ合金非磁性中間層を２５ｎｍの厚さに形成した。次に、同様に窒素を１０％添加したＡｒガス中で、放電ガス圧力２０ｍＴｏｒｒでＣｒターゲットをスパッタすることにより、窒素を含有したＣｒ合金からなる第２の非磁性中間層を形成し、他は実施例１と同様にして磁気記録媒体を形成した。
【００８６】
第２の非磁性中間層を形成後、基板が２５０℃になるように加熱されているため、酸素量は、非磁性中間層の基板側から第２の非磁性中間層の金属下地層側にかけて減少するような傾向になった。なお、基板の材料や条件によって、基板中の酸素が非磁性中間層に移動する場合もある。
【００８７】
この磁気記録媒体の１７２ｋＦＣＩ（４１．０３ＭＨｚ）と１８０ｋＦＣＩ（４２．９４ＭＨｚ）における出力及び孤立再生波の出力（ＳＬＦ）と２Ｆの媒体ノイズ（Ｎｄ）の割合ＳＬＦ／Ｎｄは、いずれも比較例１、２、３より優れていた。
【００８８】
〈実施例６〉
測定に用いた磁気ヘッドの模式的斜視図を図９に示す。基板上にＣｏ系の非晶質合金からなる下部シールド１０を設け、その後アルミナからなる第１のスペーサ２０を形成する。ＭＲ素子部１００を形成後ハードバイアスの磁区制御膜６０を形成し、電極７０を形成した。その後、再びアルミナからなる第２のスペーサ３０を形成後、スパッタ法でパーマロイ系の上部シールド９０、アルミナからなるライトギャップ部４０、レジストからなる絶縁体１３０、めっきコイル１２０、パーマロイからなる上部コア１１０を形成し、切断、アセンブリにより磁気ヘッド２０４とした。
【００８９】
次にこの磁気ヘッドを用いた磁気記憶装置の模式的斜視図を図１０に示す。この磁気記憶装置は、磁気記録媒体２０３と、これを記録方向に駆動する駆動部２０２と、記録部と再生部からなる磁気ヘッド２０４と、磁気ヘッド２０４を磁気記録媒体２０３に対して相対運動させるためのガイドアーム２０５と、磁気ヘッドへの信号入力と磁気ヘッドからの出力信号再生を行なうための記録再生信号処理回路２０１を有する。この磁気記憶装置において、磁気ヘッドの再生部が磁気抵抗効果型磁気ヘッドで構成され、磁気抵抗センサ部が互いに０．２５μｍの距離だけ隔てられた軟磁性体からなる２枚のシールド層の間に形成されており、かつ、センス電流密度を２２ＭＡ／ｃｍ²、磁気的な浮上量、すなわち、磁気記録媒体の情報記録層の表面から読み出し素子のギャップセンサー表面までの浮上高さを７２ｎｍとして、前記の磁気記録媒体について１７２ｋＦＣＩで電磁変換特性を測定した。その結果は前述の結果と定性的に同様の結果が得られた。
【００９０】
〈実施例７〉
実施例６で用いた磁気抵抗効果型磁気ヘッドの代りに、その磁気抵抗センサ部が互いに０．２μｍだけ隔てられた軟磁性体からなる２枚のシールド層の間に形成された磁気抵抗効果型磁気ヘッドを用いた他は、実施例５と同様にして磁気記録媒体の電磁変換特性を評価した。その結果、１７２ｋＦＣＩにおける出力に対する５ｋＦＣＩの孤立再生派の出力の割合は、磁気抵抗センサ部が互いに０．２５μｍだけ隔てられた軟磁性体からなる２枚のシールド層の間に形成されたヘッドを用いた場合に比べ、互いに０．２μｍだけ隔てられた軟磁性体からなる２枚のシールド層の間に形成されたヘッドを用いた場合の方が出力分解能が大きくなった。
【００９１】
〈実施例８〉
実施例６で用いた磁気抵抗効果型磁気ヘッドの代りに、互いの磁化方向が外部磁界によって相対的に変化することによって大きな抵抗変化を生じる複数の導電性磁性層と、この導電性磁性層の間に配置された導電性非磁性層を含む磁気抵抗センサによって構成される磁気ヘッドを用いた以外は、図１０と同一の構成で磁気記憶装置を構成した。測定に用いた磁気記録媒体のＢｒ×ｔは１．５、２、４、６．２、８．５、１０ｎＷｂ／ｍ（１５、２０、４０、６２、８５、１００ガウス・ミクロン）とした。Ｂｒ×ｔを１．５ｎＷｂ／ｍとした場合には、磁気記録媒体の保磁力低下が甚だしく、実用上好ましい保磁力を得ることが難しく、また１０ｎＷｂ／ｍを越えると、２Ｆの出力は大きいものの出力分解能が低下するため好ましくないことが明らかになった。
【００９２】
〈実施例９〉
外径６５ｍｍ、内径２０ｍｍ、厚さ０．６３５ｍｍのガラスディスク基板に付着した研磨材等の汚れを洗浄して乾燥させた。この基板を枚葉式直流マグネトロンスパッタ装置の基板仕込み室に装填して真空に排気した後、基板を非磁性中間層形成室、加熱室、金属下地層形成室、磁性膜形成室、保護膜形成室及び取り出し室の順に、真空度５×１０^-8Ｔｏｒｒ以下の主排気槽を介しながら搬送し、それぞれの室でそれぞれの膜を形成した。製造した磁気ディスクの断面構造は図１に示したものと同じである。
【００９３】
まず、基板を洗浄後、ＤＣインラインスパッタ装置内で加熱せずに真空状態を形成し、窒素を１０％添加したＡｒガス中で、放電ガス圧力２．６６Ｐａ（２０ｍＴｏｒｒ）でＣｒ−１０モル％ＺｒＯ₂ターゲットをスパッタすることにより優位的に酸化したＺｒと、窒素を同時に含有したＣｒ合金の非磁性中間層２’を２５ｎｍの厚さに形成した。
【００９４】
非磁性中間層を形成後の連続したプロセスでは、窒素を添加せずに、Ｃｒ−２０ａｔ．％Ｔｉ合金からなる金属下地層２を３０ｎｍの厚さに、Ｃｏ−２１．５ａｔ．％Ｃｒ−９ａｔ．％Ｐｔからなる情報記録層３を１８ｎｍの厚さに形成した。酸化物を含有した非磁性中間層２’、金属下地層２、情報記録層３等は独立した真空槽で薄膜形成することにより、容易に窒素を優位的に含まない雰囲気制御が可能となる。
【００９５】
さらに、この情報記録層３の上に１．３３Ｐａのアルゴン圧のもとでターゲットに１．５ｋＷの電力を加えて、膜厚９ｎｍの主として炭素から構成される保護膜４を形成した。そして、保護膜４上に吸着性のパーフルオロアルキルポリエーテル等の潤滑膜５を形成して２．５インチ磁気ディスクとした。
【００９６】
オージェ分析により上記非磁性中間層２’にはＣｒとＮの合計に対しておよそ１６原子％の窒素が含まれていることが確認された。また本磁気ディスクのｖＩｓは１．４×１０^-24Ｗｂ・ｍ、Ｈｃは１７８ｋＡ／ｍ、Ｈｒは１８５ｋＡ／ｍであった。
なお、合金ターゲットに含まれるＦｅ、Ｙ₂Ｏ₃等、ターゲット形成上不可避の構成元素が含まれてもなんら本発明には影響しない。
【００９７】
上記磁気ディスクについて、磁気的な浮上高さを５６ｎｍとして電磁変換特性を測定した。記録再生特性の評価には、磁気ヘッドとして、記録用にギャップ長０．３μｍ、トラック幅１．５μｍ、巻線数１７回の薄膜型ヘッド、再生用にシールド間隔０．２μｍ、トラック幅１μｍのＧＭＲヘッドを有する記録再生分離型ヘッドを用い、センス電流密度を４０ＭＡ／ｃｍ²とし、線記録密度３００ｋＦＣＩのときのＳ／Ｎｄの値を求めた。
【００９８】
５．９ｋＦＣ／ｍｍ（１５０ｋＦＣＩ）における出力は、孤立再生波の出力に対して４５％であった。また次式で示される１９７ＦＣ／ｍｍ（５ｋＦＣＩ）における孤立再生波の出力（ＳＬＦ）と１１．８ｋＦＣ／ｍｍ（３００ｋＦＣＩ）における媒体ノイズ（Ｎｄ）の割合ＳＬＦ／Ｎｄは２７．２ｄＢであった。次式でＮｄ計算時の帯域は０．５ＭＨｚから７５ＭＨｚとした。
ＳＬＦ／Ｎｄ＝２０ ｌｏｇ ［Ｅ（５ｋＦＣＩ）ｐｐ／２Ｎｄ］
また、この磁気ディスクから８ｍｍ角の試料を切り出し、信学技報（ＴＥＣＨＮＩＣＡＬ ＲＥＰＯＲＴ ＯＦ ＩＥＩＣＥ）ＭＲ９６−４（１９９６−０６）に記載の方法で記録状態の熱的安定性を表すＫＶ／ｋＴ値を測定した。その結果、この値は室温で１０３であった。
【００９９】
この磁気ディスクの再生出力について１９７ＦＣ／ｍｍ（５ｋＦＣＩ）から１１．８ｋＦＣ／ｍｍ（３００ｋＦＣＩ）における信号を記録後１分間放置してからその際の再生出力を２５回計測し、２４℃に１０５時間放置して再生出力の経時変化を測定した。１９７ＦＣ／ｍｍ（５ｋＦＣＩ）における再生出力信号はデジタルオシロスコープ（Ｔｅｋｔｒｏｎｉｘ ＴＤＳ５４４Ａ）で、１１．８ｋＦＣ／ｍｍ（３００ｋＦＣＩ）における再生信号出力はＨＰ社製スペクトラムアナライザＨＰ８５６０Ｅで測定した。いずれの線記録密度でも再生出力の減少は観測されず、出力の低下は１％未満の測定精度で認められなかった。
【０１００】
さらに本実施例における金属下地層として、Ｃｒ−Ｔｉの代わりに、Ｃｒ−１０原子％Ｍｏ、Ｃｒ−２０原子％Ｖ、Ｃｒ−２０原子％Ｎｂを用いた磁気ディスクを製造し、その特性を評価した。
【０１０１】
その結果、ｖＩｓの値は１×１０^-24Ｗｂ・ｍから１．４×１０^-24Ｗｂ・ｍであり、ＫＶ／ｋＴ値は１００〜１４０であった。Ｈｒが１６０ｋＡ／ｍ以上、１９０ｋＡ／ｍではＴｗｗ＝１．５μｍのヘッドでＯＷが４０ｄＢ以上あった。一方、Ｈｒが１９０ｋＡ／ｍを超えるとＯＷが４０ｄＢはとれなかった。
【０１０２】
〈実施例１０〉
実施例９に記載のＣｒ−１０モル％ＺｒＯ₂ターゲットに変えて、（Ｃｒ−１５ａｔ．％Ｎｂ）−１０モル％ＺｒＯ₂ターゲット、（Ｃｒ−１５ａｔ．％Ｖ）−１０モル％ＺｒＯ₂ターゲット、Ｖに（Ｖ₂Ｏ₅−ＭｏＯ₃−ＷＯ₃）の混合物を重量で１５％添加したターゲット、Ｎｂ−１０モル％ＳｉＯ₂ターゲット又は Ｃｒ−５モル％ＺｒＯ₂−５モル％Ａｌ₂Ｏ₃ターゲットを非磁性中間層として用い、情報記録層形成用のターゲットをＣｏ−２１．５ａｔ％Ｃｒ−８ａｔ％Ｐｔ、Ｃｏ−２３ａｔ．％Ｃｒ−８ａｔ．％Ｐｔ又はＣｏ−２３ａｔ．％Ｃｒ−１０ａｔ．％Ｐｔを用いた他は、すべて実施例９と同様にして媒体を形成した。
【０１０３】
この磁気ディスクのｖＩｓの値は、０．６×１０^-24Ｗｂ・ｍから１．４× １０^-24Ｗｂ・ｍであり、かつ、記録状態の熱安定性を示すＫＶ／ｋＴの値が１００よりも大きく１５０よりも小さい値であった。いずれの場合も媒体ノイズは７μＶｒｍｓよりも小さく、ＯＷが３０ｄＢ以上あり、出力低下は認められなかった。Ｈｒが１９０ｋＡ／ｍ以下で、ＫＶ／ｋＴが１３０以下の場合にはＯＷが４０ｄＢ以上あった。
【０１０４】
〈比較例４〉
実施例９と同様にして基板を洗浄後、ＤＣスパッタ装置内で加熱せずに真空状態を形成し、窒素を１０％添加したＡｒガス中で、放電ガス圧力を２．６６Ｐａ（２０ｍＴｏｒｒ）でＣｒターゲットをスパッタすることにより、窒素を含有した非磁性中間層２’を２５ｎｍの厚さに形成した他は、実施例９と同様のプロセスで磁気記録媒体を形成し、電磁変換特性を測定した。すなわち、この磁気記録媒体は非磁性中間層形成時のスパッタターゲット材料をＺｒＯ₂を含まないＣｒへ変更したものである。
【０１０５】
その結果、ｖＩｓは１．５×１０^-24Ｗｂ・ｍであり、５．９ｋＦＣ／ｍｍ（１５０ｋＦＣＩ）における出力は、孤立再生波の出力に対して４２％であった。また上式で示される１９７ＦＣ／ｍｍ（５ｋＦＣＩ）における孤立再生波の出力（ＳＬＦ）と１１．８ｋＦＣ／ｍｍ（３００ｋＦＣＩ）における媒体ノイズ（Ｎｄ）の割合ＳＬＦ／Ｎｄは２６．０ｄＢであった。
【０１０６】
これらの結果から、実施例９に比べ本比較例では、出力分解能とＳＬＦ／Ｎｄが低下することが明らかになった。
上記磁気記録媒体から８ｍｍ角の試料を切り出し、ＫＶ／ｋＴ値を測定した。その結果、この値は室温で１０１．８であった。
【０１０７】
〈比較例５〉
実施例９と同様にして基板を洗浄後、ＤＣスパッタ装置内で加熱せずに真空状態を形成し、窒素を添加しないＡｒガス中で、放電ガス圧力を２．６６Ｐａ（２０ｍＴｏｒｒ）でターゲットをスパッタすることにより、優位的に酸化したＺｒを含有したＣｒ合金からなる非磁性中間層２’を２５ｎｍの厚さに形成した他は、実施例９と同様のプロセスで磁気記録媒体を形成し、電磁変換特性を測定した。すなわち、この磁気記録媒体は、実施例９に記載のＣｒを主成分とし、酸化物を含有する非磁性中間層形成時の放電ガスから窒素を除いた場合に相当する。
【０１０８】
その結果、ｖＩｓは１．８×１０^-24Ｗｂ・ｍであり、５．９ｋＦＣ／ｍｍ（１５０ｋＦＣＩ）における出力は、孤立再生波の出力に対して３９％であった。また上式で示される１９７ＦＣ／ｍｍ（５ｋＦＣＩ）における孤立再生波の出力（ＳＬＦ）と１１．８ｋＦＣ／ｍｍ（３００ｋＦＣＩ）における媒体ノイズ（Ｎｄ）の割合ＳＬＦ／Ｎｄは２３．１ｄＢであった。
【０１０９】
これらの結果から、実施例９に比べ本比較例では、出力分解能とＳＬＦ／Ｎｄがともに低下することが明らかになった。
上記磁気記録媒体から８ｍｍ角の試料を切り出し、ＫＶ／ｋＴ値を測定した。その結果、この値は室温で１２０であった。
【０１１０】
〈比較例６〉
実施例９と同様にして基板を洗浄後、ＤＣスパッタ装置内で加熱せずに真空状態を形成し、窒素を添加しないＡｒガス中で、放電ガス圧力を２．６６Ｐａ（２０ｍＴｏｒｒ）でターゲットをスパッタすることにより、表面を優位的に酸化したＺｒを含有したＣｒ合金からなる非磁性中間層２’を２５ｎｍの厚さに形成し、さらに情報記録層の組成をＣｏ−２３ａｔ．％Ｃｒ−７ａｔ．％Ｐｔに変更した他は、実施例９と同様のプロセスで磁気ディスクを形成し、磁気的な浮上量を５６ｎｍ、６２ｎｍとして電磁変換特性を測定した。
【０１１１】
その結果、ｖＩｓは１．１５×１０^-24Ｗｂ・ｍであり、前述の式で示される１９７ＦＣ／ｍｍ（５ｋＦＣＩ）における孤立再生波の出力（ＳＬＦ）と１０．２ｋＦＣ／ｍｍ（２６０ｋＦＣＩ）における媒体ノイズ（Ｎｄ）の割合ＳＬＦ／Ｎｄは、各浮上量に対してそれぞれ３０．９７、３０．０９ｄＢであった。
【０１１２】
上記磁気ディスクから８ｍｍ角の試料を切り出し、記録状態の熱的安定性をあらわすＫＶ／ｋＴ値を測定した。その結果、この値は室温で１００であった。この磁気ディスクに１９７ＦＣ／ｍｍ（５ｋＦＣＩ）から１０．２ｋＦＣ／ｍｍ（２６０ｋＦＣＩ）の信号を記録後、これらの信号記録密度における再生出力の時間変化を観測した。その結果４日間経過時点で磁気的な浮上量を６２ｎｍとした場合、図１１に示すように、１９７ＦＣ／ｍｍ（５ｋＦＣＩ）の再生出力は４％程度減少した。また、１０．２ｋＦＣ／ｍｍ（２６０ｋＦＣＩ）における再生出力は磁気的な浮上量を５６から６２ｎｍとした場合約８％減少していることが明らかになった。
【０１１３】
こうして形成した磁気ディスクの静磁気特性（保磁力Ｈｃ、角形比Ｓ＊）を以下の方法により評価した。静磁気特性は、上記磁気ディスクを、その半径２０ｍｍの位置から８ｍｍ×８ｍｍの略正方形状に切り出し、片面の磁性膜を削り落とした試料を作製し、振動試料型磁力計（ＶＳＭ）を用いて最大印加磁界を１３ｋＯｅとして面内方向の静磁気特性を求めた。この媒体の磁気特性は以下の通りである。保磁力は１６０ｋＡ／ｍ（２．０ｋＯｅ）、Ｂｒｔ＝６．７９ｎＷｂ／ｍ、Ｓ＊＝０．５９， Ｓ＝０．６４であった。
【０１１４】
〈実施例１１〉
実施例９と同様にして基板を洗浄後、ＤＣスパッタ装置内で加熱せずに真空状態を形成し、窒素を添加したＡｒガス中で、放電ガス圧力を２．６６Ｐａ（２０ｍＴｏｒｒ）でターゲットをスパッタすることにより、表面を優位的に酸化したＺｒを含有したＣｒ合金中間層Ａ２’を２５ｎｍの厚さに形成し、さらに情報記録層の組成をＣｏ−２３ａｔ．％Ｃｒ−７ａｔ．％Ｐｔに変更した他は、実施例９と同様のプロセスで磁気ディスクを形成し、磁気的な浮上量を５６ｎｍ、６２ｎｍとして電磁変換特性を測定した。
【０１１５】
その結果、ｖＩｓは１．２×１０^-24Ｗｂ・ｍであり、前述の式で示される１９７ＦＣ／ｍｍ（５ｋＦＣＩ）における孤立再生波の出力（ＳＬＦ）と１０．２ｋＦＣ／ｍｍ（２６０ｋＦＣＩ）における媒体ノイズ（Ｎｄ）の割合ＳＬＦ／Ｎｄは各浮上量に対してそれぞれ３１．１９、２９．８７ｄＢであった。
【０１１６】
上記磁気ディスクから８ｍｍ角の試料を切り出し、記録状態の熱的安定性を表すＫＶ／ｋＴ値を測定した。その結果、この値は室温で１１０．４であった。
【０１１７】
この磁気ディスクに１９７ＦＣ／ｍｍ（５ｋＦＣＩ）から１０．２ｋＦＣ／ｍｍ（２６０ｋＦＣＩ）の信号を記録後、これらの信号記録密度における再生出力の時間変化を観測した。その結果４日間経過時点で磁気的な浮上量を６２ｎｍとした場合１９７ＦＣ／ｍｍ（５ｋＦＣＩ）と１０．２ｋＦＣ／ｍｍ（２６０ｋＦＣＩ）における再生出力は磁気的な浮上量を５６から６２ｎｍとした場合に認められないことが明らかになった。
【０１１８】
こうして形成した磁気ディスクの静磁気特性は以下の通りである。保磁力は１７６ｋＡ／ｍ（２．２ｋＯｅ）、Ｂｒｔ＝７．２１ｎＷｂ／ｍ、Ｓ＊＝０．６５、Ｓ＝０．７０であった。
【０１１９】
〈実施例１２〉
非磁性中間層の材料を変えて試作した媒体のＸ線回折曲線を図１２に示す。測定は理学電機株式会社製Ｘ線回折装置ＲＩＮＴによる。銅の回転対陰極を用い、電流を１００から１６０ｍＡ、加速電圧を５０ｋＶとした。サンプリング幅を０．０２度、走査速度を２度／分、発散スリットを１度、散乱スリットを１度、受光スリットを０．３ｍｍとした。モノクロメータを使用し、モノクロメータ受光スリットを０．４５ｍｍとした。走査角度の範囲を２θで３０度から９０度までとしてθ−２θ走査を行なった。
【０１２０】
測定に用いた試料構成は、表面から、Ｃ保護膜／Ｃｏ−Ｃｒ−Ｐｔ情報記録層（厚さ１５ｎｍ）／Ｃｒ−Ｔｉ金属下地層（厚さ３０ｎｍ）／Ｃｒ−（ＺｒＯ₂）非磁性中間層（厚さ２５ｎｍ）／化学強化ガラス基板である。
【０１２１】
回折曲線の低角側から、（１）ｈｃｐ構造をとる（Ｃｏ−Ｃｒ−Ｐｔ）情報記録層の１０・０回折ピーク、（２）ｂｃｃ構造をとる（Ｃｒ−Ｔｉ）金属下地膜の１１０回折ピーク、（３）同じくｂｃｃ構造をとる非磁性中間層の１１０回折ピーク、（４）ｈｃｐ構造をとる（Ｃｏ−Ｃｒ−Ｐｔ）情報記録層の１０・１回折ピークが認められた。これらの回折ピークのうち、（２）の（Ｃｒ−Ｔｉ）金属下地膜による回折強度がもっとも大きい。（１）〜（４）以外の回折ピークは走査した範囲（３０〜９０度）で見出せなかった。ｈｃｐ構造をとる（Ｃｏ−Ｃｒ−Ｐｔ）情報記録層の１０・０回折ピークが認められたことから、金属下地膜中に２１１配向した微結晶が存在する可能性がある。
【０１２２】
図中Ａで示す回折曲線は、比較例であって、非磁性中間層を酸化物を含まないＣｒを低ガス圧力（１．０６Ｐａ）のＡｒ（Ｎ₂を含まない）で形成した場合、図中Ｂで示す回折曲線は、比較例であり、非磁性中間層を酸化物を含まないＣｒを高ガス圧力（２．６６Ｐａ）のＡｒ（Ｎ₂を含まない）で形成した場合、
図中Ｃで示す回折曲線は、比較例であり、非磁性中間層を酸化物を含まないＣｒを高ガス圧力（２．６６Ｐａ）の１０容量％窒素を添加したＡｒで形成した場合、
図中Ｄで示す回折曲線は、実施例であり、非磁性中間層をＺｒＯ₂を含むＣｒを高ガス圧力（２．６６Ｐａ）の１０容量％窒素を添加したＡｒで形成した場合、図中Ｅで示す回折曲線は、比較例であり、非磁性中間層をＺｒＯ₂を含むＣｒを高ガス圧力（２．６６Ｐａ）のＡｒ（Ｎ₂を含まない）で形成した場合である。
【０１２３】
非磁性中間層を低ガス圧力（１．０６Ｐａ）で形成した場合（Ａ）、最も結晶性が高い。非磁性中間層を高ガス圧力（２．６６Ｐａ）のＡｒで形成した場合（Ｂ）は、（Ａ）に比べて非磁性中間層と金属下地層の回折強度は低下し、結晶性は低下した。さらに放電ガス中に１０容量％窒素を添加すると（Ｃ）、さらに結晶性が低下し、特に非磁性中間層の回折強度が減少した。
【０１２４】
（Ｃｒ−ＺｒＯ₂）非磁性中間層を高ガス圧力（２．６６Ｐａ）のＡｒで形成した場合（Ｅ）、酸化物を含まないＣｒの非磁性中間層の場合（Ｂ）に比べ、非磁性中間層と金属下地層の回折強度は低下し、結晶性は一層低下した。さらに、放電ガス中に１０容量％窒素を添加した場合（Ｄ）、金属下地層の回折強度は減少した。
【０１２５】
いずれの非磁性中間層形成条件でもｈｃｐ構造をとる情報記録層の１０・０及び１０・１回折ピークが観測され、非磁性中間層や金属下地層の結晶性が低下するとＣｏ１０・０の配向性がわずかに増加した。
【０１２６】
以上の測定結果から、比較的結晶性の高い高い系として窒素を添加しないＡｒだけで中間層を形成した系を選択して、非磁性中間層の結晶性を調べた。測定に用いる特性Ｘ線の波長をλ、回折曲線の半値幅をＢ［ｒａｄ］、半値幅を測定する回折ピークの角度を２θ_Bとすると次式で示すＳｃｈｅｒｒｅｒの式により中間層の結晶粒径ｔが予備的に評価できる。
【０１２７】
ｔ ＝ ０．９λ・ｃｏｓ（２θ_B）
Ａｒ放電ガス圧力を変えて形成したＣｒ及び（Ｃｒ−ＺｒＯ₂）非磁性中間層の１１０回折曲線を図１３に示す。放電ガス圧力の増加に伴い、Ｃｒのみの非磁性中間層の１１０回折強度は減少した。（Ｃｒ−ＺｒＯ₂）非磁性中間層の１１０回折強度は放電ガス圧力によらずＣｒのみの非磁性中間層の１１０回折強度より弱い。非磁性中間層の１１０回折ピークから格子定数と放電ガス圧力の関係を求めたところ、放電ガス圧力の増加に伴い格子定数は増加した。放電ガス圧力によらず、（Ｃｒ−ＺｒＯ₂）非磁性中間層の格子定数はＣｒのみの非磁性中間層の格子定数よりもわずかに大きい。
【０１２８】
放電ガス圧力を変えて形成したＣｒ及び（Ｃｒ−ＺｒＯ₂）非磁性中間層の１１０回折ピークの半値幅と放電ガス圧力の関係を図１４に示す。放電ガス圧力の増加に伴い、非磁性中間層の１１０回折ピークの半値幅は増加した。放電ガス圧力によらず、（Ｃｒ−ＺｒＯ₂）非磁性中間層の１１０回折ピークの半値幅は、Ｃｒのみの非磁性中間層の半値幅よりも大きい。この傾向に対応して（Ｃｒ−ＺｒＯ₂）非磁性中間層の結晶粒径はＣｒのみの非磁性中間層のおよそ半分程度の４から８ｎｍと予想される（図１５）。窒素を添加した系では図１２にも示したようにさらに結晶性が低下しており、結晶粒が微細化していると考えられる。
【０１２９】
【発明の効果】
以上述べたように、本発明の磁気記録媒体は、金属下地層と基板の接着強度を向上させたまま、高線記録密度における高い出力分解能を示し、雑音に対する出力の割合が増加した。また、本発明の磁気記憶装置は、このような磁気記録媒体を用いるのに適していた。
【図面の簡単な説明】
【図１】本発明の磁気記録媒体の断面模式図。
【図２】１７２ｋＦＣＩで測定したＳＬＦ／Ｎｄと出力分解能Ｒｅの関係を示す図。
【図３】１８０ｋＦＣＩで測定したＳＬＦ／Ｎｄと出力分解能Ｒｅの関係を示す図。
【図４】１７２ｋＦＣＩで測定したＮｄと活性化磁気モーメントの関係を示す図。
【図５】１８０ｋＦＣＩで測定したＮｄと活性化磁気モーメントの関係を示す図。
【図６】１７２ｋＦＣＩで測定したＳ／Ｎｄと出力分解能Ｒｅの関係を示す図。
【図７】１８０ｋＦＣＩで測定したＳ／Ｎｄと出力分解能Ｒｅの関係を示す図。
【図８】活性化磁気モーメントと窒素添加濃度の関係を示す図。
【図９】磁気ヘッドの断面構造の一例を示す斜視図。
【図１０】本発明の磁気記憶装置の模式図。
【図１１】記録直後に出力に対する出力の経時変化を示す図。
【図１２】磁気記録媒体のＸ線回折曲線を示す図。
【図１３】非磁性中間層のＸ線回折曲線を示す図。
【図１４】１１０回折ピークの半値幅を示す図。
【図１５】１１０回折ピークの半値幅から求めた粒径を示す図。
【符号の説明】
１…非金属基板
２…金属下地層
２’…中間層
３…磁性膜
４…保護膜
５…潤滑膜
１０…下部シールド
２０…第１のスペーサ
３０…第２のスペーサ
４０…ライトギャップ
６０…磁区制御膜
７０…電極
９０…上部シールド
１００…ＭＲ素子部
１１０…上部コア
１２０…めっきコイル
１３０…絶縁体
２０１…記録再生信号処理回路
２０２…駆動部
２０３…磁気記録媒体
２０４…磁気ヘッド
２０５…ガイドアーム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording medium capable of recording large-capacity information and a magnetic storage device using the same, and more particularly to a magnetic recording medium suitable for high-density magnetic recording and a small-capacity magnetic storage device using the same. .
[0002]
[Prior art]
The demand for larger capacity for magnetic storage devices is now increasing. As a conventional magnetic head, an electromagnetic induction type magnetic head using a voltage change accompanying a temporal change of magnetic flux has been used. With this head, both recording and reproduction can be performed with one head. On the other hand, in recent years, the adoption of a composite type head using a magnetoresistive head having a higher sensitivity for reproduction has been rapidly progressing. In order to improve the sensitivity of the magnetoresistive head utilizing the fact that the electric resistance of the head element changes according to the change of the leakage magnetic flux from the medium, it is generated in a magnetic layer of a type in which a plurality of magnetic layers are stacked via a nonmagnetic layer. Development of a head with higher sensitivity utilizing a very large magnetoresistance change (giant magnetoresistance effect or spin valve effect) is also in progress. This utilizes the fact that the relative magnetization direction of a plurality of magnetic layers through the nonmagnetic layer changes due to the leakage magnetic field from the medium, and the magnetoresistance changes.
[0003]
On the other hand, a magnetic recording medium for in-plane magnetic recording that records magnetization in the in-plane direction uses a Co-based alloy-based magnetic thin film mainly composed of a ferromagnetic metal such as Co as an information recording layer. In order to increase the recording density of the information recording layer, it is required to (1) increase the coercive force (Hc), (2) reduce the medium noise, and (3) improve the durability.
[0004]
In order to increase the coercive force (Hc), for example, the amount of Pt added in the CoCrPt alloy magnetic film is increased, and this is applied to an alloy-based non-magnetic material having a body-centered cubic (bcc) Cr or Cr as a main component. A method of epitaxial growth on the ground film is described in Journal of Applied Physics, Vol. 73 (1993), pages 5569 to 5571 (J. Appl. Phys., Vol. 73, (1993) pp. 5569 to 5571). ing.
[0005]
In order to realize high-density recording, in order to overcome the demagnetizing field from the magnetic charge at the bit boundary and maintain the magnetization in the recording direction, the coercive force is increased and at the same time the film thickness t of the information recording layer It is necessary to reduce the product Br · t of the residual magnetic flux density Br to reduce the demagnetizing field. IEE Transactions on Magnetics, Vol. 29 (1993), pages 3670 to 3672 (IEEE) Trans. On Magn., Vol. 29, No. 6 (1993) p. 3670-3672).
[0006]
On the other hand, as a technique for reducing the medium noise, a non-magnetic underlayer mainly composed of two layers of Cr is formed, and the first underlayer disposed on the substrate side has a body-centered cubic structure in X-ray diffraction. A nonmagnetic underlayer having a crystal structure mainly composed of (110) orientation is formed to a thickness of 0.5 to 8 nm, and a second nonmagnetic underlayer mainly composed of (200) orientation having a body-centered cubic structure is formed thereon. Japanese Patent Laid-Open No. 7-57238 describes a method for forming a film with a thickness of 20 to 300 nm.
[0007]
In order to reduce the medium noise, it is effective to reduce the crystal grain size of the magnetic film to reduce the activation magnetic moment vIs. Journal of Applied Physics Vol. 79, No. 8, 5351 Page (J. Appl. Phys., Vol. 79 (8), 15 April 1996, pp. 5351-5353). Here, v is the volume of the smallest unit (cluster) of magnetization reversal, and Is is the spontaneous magnetization of the magnetic part in the magnetic film. By reducing the crystal grains of the magnetic film, v can be reduced.
[0008]
Japanese Patent Laid-Open No. 8-77543 discloses a technique for increasing the fluctuation field (Hf) with a magnetic field strength equal to the remanent coercive force or coercive force by reducing the crystal grains of the magnetic recording medium in order to reduce the medium noise. Has been proposed.
[0009]
Furthermore, in order to reduce medium noise and improve durability, the underlayer is multilayered so that the underlayer on the magnetic layer side has a function of reducing noise, and the magnitude of the output signal against noise is increased. The base layer on the substrate side has good adhesion to the nonmagnetic support to improve durability against contact start / stop, and the base layer on the substrate side is provided on the base layer on the magnetic layer side. A gas barrier that absorbs moisture and other gases that are released from the substrate when the magnetic layer and protective layer are sequentially formed, and that adversely affects the magnetic properties, so that the gas does not reach the underlayer or magnetic layer on the magnetic layer side. A technology has been proposed.
[0010]
That is, the technique described in Japanese Patent Application Laid-Open No. 62-293511 is a magnetic recording medium in which a metal underlayer and a magnetic layer are deposited on a nonmagnetic nonmetal substrate, the substrate and the metal underlayer. And an oxide of a metal containing at least one element of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, and the oxygen concentration in the thickness direction is a metal underlayer It relates to an intermediate layer having a characteristic of decreasing continuously or stepwise in the direction.
[0011]
In addition, the technique described in Japanese Patent Application Laid-Open No. 62-293512 is a magnetic recording medium in which a metal underlayer and a magnetic layer are laminated on a nonmagnetic nonmetal substrate, and the substrate and the metal underlayer And an oxide of a metal containing at least one element of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, and the oxygen concentration in the thickness direction is in the direction of the metal underlayer And a metal or alloy containing at least one element selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. The present invention relates to an intermediate layer in which layers are sequentially stacked.
[0012]
In addition, as a method for improving the S / N ratio and improving the magnetostatic characteristics and electromagnetic conversion characteristics, there is a technique for improving crystal orientation by adding oxygen to a nonmagnetic underlayer mainly composed of Cr. 1-290118.
[0013]
Further, an example using a chromium (Cr) underlayer added with nitrogen between the substrate and the magnetic layer is described in Journal of Applied Physics, Vol. 63 No. 8 (April 15, 1988), page 3269 (J. Appl. Phys). , Vol.63, No.8, (1988) p.3269). In this case, by adding nitrogen to the underlayer, the easy magnetization axis of the cobalt alloy magnetic layer to be formed later is easily oriented in the direction perpendicular to the film surface, and the coercivity measured in the in-plane direction is reduced. It has been shown that it is not preferable to use a Cr underlayer with nitrogen added between the substrate and the magnetic layer as the magnetic recording medium.
Similarly, an example using a Cr underlayer with nitrogen added between the substrate and the magnetic layer is also described in JP-A-4-64914.
[0014]
[Problems to be solved by the invention]
Prior art described in the above Japanese Patent Publication No. 7-101502, that is, a metal oxide containing Cr between the substrate and the metal underlayer, and the oxygen concentration in the thickness direction is continuous or stepwise in the direction of the metal underlayer The magnetic recording medium having an intermediate layer having a characteristic that decreases as a result has a problem that as the linear recording density is increased, the output resolution is lowered and the ratio of output to noise is also lowered at the same time. Here, the output resolution is an index indicating the ratio of the output of the isolated reproduction wave to the reproduction output of the signal recorded at the linear recording density assumed for the magnetic recording medium used in the magnetic storage device.
[0015]
Moreover, the prior art described in the above-mentioned JP-A-7-57238 must control the film thickness with a thickness of 0.5 to 8 nm, and it is difficult to control the film thickness as a mass-produced product. There was a problem. Desirably, the thickness of each layer is preferably at least 10 nm.
[0016]
The prior art described in the above-mentioned Japanese Patent Application Laid-Open No. 8-77543 has low reproduction noise and high S / N. However, the temperature change rate of the coercive force increases, and the performance of the magnetic storage device depends on the temperature. There was a problem of changing. In order to keep the performance of the magnetic storage device within a certain range in various environments, it is necessary to reduce the rate of change of the coercivity of the magnetic recording medium with respect to the ambient temperature. When Hf is increased and the medium noise is reduced in this way, the temperature change rate of the coercive force tends to increase. This is because in a magnetic recording medium having a large Hf, the frequency of magnetization reversal by an external magnetic field strongly depends on the ambient temperature.
[0017]
The magnetoresistive head described above is very high in reproduction sensitivity and is suitable for high recording density. However, not only the reproduction signal from the magnetic recording medium but also the sensitivity to noise is increased at the same time. For this reason, magnetic recording media are required to have lower noise than before.
[0018]
In addition, other conventional techniques also adopt a configuration suitable for mass production while increasing the ratio of output to noise with high output resolution at high linear recording density while improving the adhesive strength between the metal underlayer and the substrate. There was a problem that it was difficult.
[0019]
Furthermore, there is a problem that all of the above prior arts do not consider thermal fluctuations. Thermal fluctuation is the effect of temperature on the magnetic anisotropy when the volume v, the minimum unit of magnetization reversal, becomes small, and once recorded, the magnetization is reversed by the influence of the demagnetizing field with a certain probability. It means to end. In general, the effect is represented by KV / kT, and the smaller the value, the greater the influence of thermal fluctuation. This is described, for example, in TECHNICICAL REPORT OF IEICE MR96-4 (1996-06). Here, K is the magnetic anisotropy constant of the magnetic grains in the magnetic film, V is the volume of the magnetic grains, k is the Boltzmann constant, and T is the absolute temperature. Conventionally, as a result of media noise reduction, the value of V has decreased, and in order to keep KV / kT constant, it is necessary to increase the value of K. However, in order to increase the value of K, it is necessary to improve Hc and the residual coercive force Hr. At this time, overwriting (OW) of 30 dB or more becomes difficult with a magnetic head having a recording track width Tww of less than 1.5 μm. For this reason, there has been no known method for solving both the low noise and thermal fluctuation problems.
[0020]
A first object of the present invention is to increase the ratio of output to noise with high output resolution at a high linear recording density while improving the adhesive strength between the metal underlayer and the substrate, and suitable for mass production. It is to provide a recording medium.
A second object of the present invention is to provide a magnetic storage device suitable for using such a magnetic recording medium.
[0021]
[Means for Solving the Problems]
In order to achieve the first object, the magnetic recording medium of the present invention includes a first element group consisting of Ti, Zr, Hf, V, Nb, Ta, Mo, W, Si, and Al on a substrate. An information recording comprising an oxide of at least one selected element, a second element made of Cr, and a nonmagnetic intermediate layer containing nitrogen, and comprising a metal underlayer and a Co-based alloy-based magnetic film thereon Layers are arranged.
[0022]
It is preferable that the nonmagnetic intermediate layer of the magnetic recording medium further includes at least one element selected from the first element group. Further, when the nonmagnetic intermediate layer is manufactured using an alloy target, Fe, Y ₂ O _Three Such a constituent element that is unavoidable for target formation may be contained in the nonmagnetic intermediate layer.
[0023]
The amount of the oxide is preferably in the range of 5 mol% to 70 mol% of the total amount with the second element, Cr, as a compound having a stoichiometric amount of oxygen, and 5 mol%. Is more preferably in the range of from 50 to 50 mol%. A compound having a stoichiometric amount of oxygen is, for example, ZrO when the selected first element is Zr. ₂ It is. That is, the compound in the nonmagnetic intermediate layer of the oxide is ZrO. ₂ When ZrO _2-x And sometimes it is a mixture of both. However, when calculating the amount of oxide, all the oxygen is ZrO. ₂ Calculated as present in the compound.
[0024]
In order to achieve the first object, the magnetic recording medium of the present invention is a first recording medium comprising Ti, Zr, Hf, V, Nb, Ta, Mo, W, Si, Al and Y on a substrate. An oxide of at least one element selected from the group of elements, a second element consisting of Cr or V, and a nonmagnetic intermediate layer containing at least nitrogen, on which a metal underlayer and a Co-based alloy system An information recording layer made of a magnetic film is arranged.
[0025]
It is preferable that the nonmagnetic intermediate layer of the magnetic recording medium further includes at least one element selected from the first element group. When the nonmagnetic intermediate layer is manufactured using an alloy target, the nonmagnetic intermediate layer may contain an element inevitable for forming the target such as Fe. Further, the amount of the oxide is preferably in the range of 5 mol% to 70 mol% of the total amount with the second element composed of Cr or V as a compound having a stoichiometric amount of oxygen, More preferably, it is in the range of 5 mol% to 50 mol%.
[0026]
When the second element is V, the nonmagnetic intermediate layer of the magnetic recording medium preferably contains at least 1 mol% or more of an element other than V as the first element, and more preferably contains 5 mol% or more. . Most preferably, the first element is composed of an element other than V.
[0027]
In order to achieve the first object, the magnetic recording medium of the present invention includes a first element comprising Ti, Zr, Hf, Nb, Ta, Mo, W, Si, Al, and Y on a substrate. An oxide of at least one element selected from the group, a second element composed of Nb, and a nonmagnetic intermediate layer containing at least nitrogen are disposed, and a metal underlayer and a Co-based alloy magnetic film are formed thereon. An information recording layer is arranged.
[0028]
The nonmagnetic intermediate layer of this magnetic recording medium preferably contains at least 1 mol% or more of an element other than Nb as the first element, and more preferably contains 5 mol% or more. Most preferably, the first element is composed of an element other than Nb. The nonmagnetic intermediate layer preferably further includes at least one element selected from the first element group. When the nonmagnetic intermediate layer is manufactured using an alloy target, the nonmagnetic intermediate layer may contain an element inevitable for forming the target such as Fe. The amount of the oxide is preferably in the range of 5 mol% to 70 mol% of the total amount with the second element Nb as a compound having a stoichiometric amount of oxygen. More preferably, it is in the range of 50% to 50% by mole.
[0029]
In any case, if the amount of the oxide is less than 5 mol%, the crystal grains are difficult to become fine. When the amount of the oxide is 5 mol% or more, a microcrystalline structure or an amorphous structure tends to be obtained. The nitrogen concentration is 0.1 at. With respect to the total of the second element and N. % To 50 at. % Range is preferred and 1 at. % To 50 at. % Range is more preferred.
[0030]
The nonmagnetic intermediate layer may have a structure in which the oxygen concentration in the thickness direction decreases continuously or stepwise in the direction of the metal underlayer or a combination of both. At this time, the metal underlayer side of the nonmagnetic intermediate layer may have a portion not containing oxygen. That is, the structure may be such that the oxygen concentration in the thickness direction is high on the substrate side, decreases toward the metal underlayer, and there is a portion where the oxygen concentration becomes zero.
[0031]
Such a structure will be described. A metal underlayer exists on the nonmagnetic intermediate layer (on the side opposite to the substrate). As will be described later, the metal underlayer is preferably body-centered cubic Cr or Cr alloy, and the Cr alloy is an alloy such as Ti or Zr. When such a structure is used, oxygen in the oxide of the nonmagnetic intermediate layer may move to the metal underlayer depending on manufacturing conditions, thereby forming an element and an oxide constituting the alloy. For this reason, the properties of the metal underlayer change, and for example, a body-centered cubic structure may not be adopted. At this time, if a Cr alloy layer is formed as a second non-magnetic intermediate layer on the non-magnetic intermediate layer and oxygen is moved up to the second non-magnetic intermediate layer, the non-magnetic intermediate layer is formed. The metal underlayer can maintain desired properties. In this way, a structure is obtained in which the oxygen concentration in the thickness direction of the nonmagnetic intermediate layer is high on the substrate side and decreases toward the metal underlayer.
[0032]
Furthermore, in any case, the nonmagnetic intermediate layer preferably has a thickness in the range of 10 nm to 500 nm, and more preferably in the range of 10 nm to 50 nm. When the thickness of the intermediate layer is less than 10 nm, it is generally necessary to form a thin film in an extremely short time of about several seconds, and it is difficult to control the film thickness. It is easy to do, and it is difficult to make it uniform thickness. In order to increase the efficiency during mass production, the film thickness is preferably 500 nm or less, and more preferably 50 nm or less.
[0033]
The first element such as Ti, Zr, and Hf is more likely to be oxidized than the second element such as Cr. Therefore, if the amount of oxygen is sufficient, it exists mainly in the form of an oxide. On the other hand, nitrogen reacts with a second element such as Cr and exists in the form of a nitride or in the form of a nitrogen-containing solid solution. Depending on the amount of the second element, it may exist in the form of a nitride of the first element.
[0034]
The nonmagnetic intermediate layer containing these oxides is recognized as amorphous or microcrystalline from X-ray diffraction. When it is a microcrystal, a crystal grain mainly containing a second element such as Cr contains nitrogen, and further contains an oxide of a first element such as Ti, Zr, or Hf as a main ingredient. It is presumed that there is an effect of suppressing the grain growth at the time of crystal growth by adopting a structure in which the portion having a different phase is segregated at the grain boundary of the crystal grain and the crystal grain is uniformly refined. It is preferable that these oxides are segregated in the film because the medium noise and the thermal fluctuation can be reduced at the same time.
[0035]
On the other hand, in any case, the metal underlayer is preferably Cr or a Cr alloy and has a body-centered cubic structure (bcc structure). Further, it preferably has a crystal structure mainly composed of (hkk) orientation, for example, (100) orientation where h = 1 and k = 0. The metal underlayer may contain at least one element selected from Ti, Zr, Hf, V, Nb, Ta, Mo, W, Si, Al, and the like. In particular, it is preferable to include at least one element of Ti, V, Nb, and Mo. Among these elements, small elements such as Ti and Si are about 25 at. %, Zr and Hf, which do not take a body-centered cubic structure alone, are approximately 10 at. %, 5 at. It is preferable to contain up to about% in order to maintain the body-centered cubic structure. The above values are approximate, and it is well known that the exact values for each element depend on the manufacturing method.
[0036]
As described above, the metal underlayer is made of body-centered cubic (bcc) Cr or an alloy containing Cr as a main component, and the size of the (110) crystal lattice is set to Co of hexagonal close-packed structure (hcp). 4 Gb / in when substantially matched with the size of the (10 · 1) crystal lattice of the information recording layer of the base alloy system ² It is preferable because sufficient reproduction output can be obtained even at the above high recording density. Here, the size of the crystal lattice of the metal underlayer substantially matches the size of the crystal lattice of the information recording layer as long as the difference in the size of the crystal lattice is in the range of about ± 5%. Means that. In particular, when the metal underlayer is made of Cr—Ti or Cr—Mo alloy, and the additive concentration of Ti or Mo is 10-30 atomic%, the crystal lattice consistency with the information recording layer of Co—Cr—Pt alloy In addition, the crystal grain size can be reduced with the increase in the medium noise, which is preferable because the medium noise can be reduced. When the addition concentration exceeds 30%, the activation magnetic moment vIs is 1.5 × 10 ^{-twenty four} It becomes larger than Wb · m, and as a result, medium noise may increase, which is not preferable.
[0037]
The metal underlayer can also increase the proportion of crystal grains that are oriented and grown so that the (10.0) plane in the crystal grains of the information recording layer is parallel to the substrate. As a result, the c-axis, which is the easy axis of magnetization of the magnetic film, becomes parallel to the substrate surface, and 4 Gb / in ² Sufficient reproduction output can be obtained even at the above high recording density.
[0038]
The thickness of the metal underlayer is preferably 10 nm or more and 500 nm or less, and more preferably 10 nm or more and 50 nm or less for the same reason as the thickness of the nonmagnetic intermediate layer.
[0039]
In any case, the information recording layer made of a Co-based alloy magnetic film has a film thickness t of 10 nm or more and 30 nm or less and a coercive force Hc of 150 kA / m or more. This is preferable because the width of the magnetization transition region decreases and a high output can be obtained even in a high recording density region. Further, in order to ensure good overwriting (overwrite, OW) characteristics of 30 dB or more, the coercive force Hc is preferably set to 320 kA / m or less. OW was measured according to the following definition. It is defined by the ratio between the fundamental wave component E1Fi of the low frequency signal written first and the residual E1Fr of E1Fi when overwritten with the high frequency signal E2F. Ie
OW = -20log (E1Fr / E1Fi)
The frequency of the high frequency signal E2F was made to correspond to the assumed maximum linear recording density. The frequency of the low frequency signal E1Fi is 1/6 of the high frequency signal E2F.
[0040]
Further, the product (Brt) of the residual magnetic flux density Br and the thickness t measured by applying a magnetic field in the relative running direction of the magnetic head with respect to the magnetic recording medium at the time of recording is 2 nWb / m (20 gauss microns) or more. It is preferably 10 nWb / m (100 Gauss · micron) or less, and more preferably 2 nWb / m or more and 8 nWb / m or less. This is because the medium noise is reduced and a high medium S / N is obtained.
[0041]
The activation magnetic moment vIs is 0.6 × 10 ^{-twenty four} From Wb · m 1.4 × 10 ^{-twenty four} Wb · m is preferable. Further, if the value of KV / kT, which indicates the thermal stability of the recording state, is 100 or more, the medium noise is small, and the reduction in reproduction output is 3% or less even after being left at 24 ° C. for 105 hours after magnetic recording. Therefore, it is preferable. Further, the value of KV / kT is preferably 150 or less because the medium noise is reduced and the overwrite can be set to 30 dB. In particular, when KV / kT is 130 or less and the residual coercive force Hr is 190 kA / m or less, even a magnetic head having a recording track width Tww of 1.5 μm or less can achieve an overwrite of 40 dB or more. The residual coercive force Hr is preferably 160 kA / m or more.
[0042]
The information recording layer is composed of two or more layers, and at least one of Cr, Mo, W, V, Ta, Nb, Zr, Ti, B, Be, C, Ni-P, NiAl, and oxygen is provided between the layers. As a main component, a nonmagnetic layer having a film thickness of 0.5 nm or more and 2 nm or less may be provided. In general, medium noise is further reduced as compared with a single information recording layer.
[0043]
In order to achieve the first object, the magnetic recording medium of the present invention has an information recording layer made of a Co-based alloy-based magnetic film on a substrate with at least one underlayer interposed therebetween, The product (Br × t) of the thickness t of this information recording layer and the residual magnetic flux density Br is 2 nWb / m or more and 8 nWb / m or less, and the activation magnetic moment is 0.6 × 10. ^{-twenty four} Wb · m or more, 1.4 × 10 ^{-twenty four} Wb · m or less, and the value of KV / kT is 100 or more and 150 or less.
[0044]
In this magnetic recording medium, the value of KV / kT is preferably 100 or more and 130 or less. The residual coercive force of the information recording layer is preferably 160 kA / m or more and 190 kA / m or less. Further, it is preferable that this magnetic recording medium has no decrease in reproduction output after being left at 24 ° C. for 105 hours after recording, or 3% or less.
[0045]
Further, in any magnetic recording medium, when the center line average roughness Ra of the surface of the medium protective film measured in the direction perpendicular to the head running direction is 0.3 nm or more and 3 nm or less, the head flying height is 0. A thickness of 0.02 μm or more and 0.1 μm or less is preferable because it floats stably. When Ra on the surface of the medium is set to a value smaller than the conventional value, it is preferable to prevent sticking of the magnetic head during CSS (contact start / stop) operation. Therefore, for example, after forming a protective film on the information recording layer, plasma etching is performed using a mask to form fine irregularities with a height of 20 nm or less on the surface, or a low melting point metal compound such as Al-Cr. When the mixture target is used to form fine protrusions on the surface of the protective film, or fine irregularities are formed on the surface by heat treatment, the frictional force between the magnetic head and the medium can be reduced during CSS operation. This is preferable because the problem of sticking to the medium is avoided.
[0046]
Furthermore, in any magnetic recording medium, a nonmagnetic material having a film thickness of 3 to 20 nm is mainly formed as a protective layer on the information recording layer, and carbon, hydrogenated carbon or carbon is used as a protective layer. Providing a lubricating layer of alkyl polyether or the like with a film thickness of 1 to 5 nm is preferable because a magnetic recording medium with high reliability and high-density recording can be obtained.
[0047]
For the protective layer, carbides such as WC, (W-Mo) -C, (Zr-Nb) -N, Si _Three N _Four Nitride such as SiO ₂ , ZrO ₂ Oxides such as B or B _Four C, MoS ₂ , Rh or the like is preferable because it can improve sliding resistance and corrosion resistance. The surface of these protective films is etched using a mask, and protrusions with an area ratio of 1 to 20% are provided, or film formation conditions, compositions, etc. are adjusted to deposit protrusions of different phases in the protective film. Thus, it is more preferable that the protective film has a larger surface roughness than the surface of the magnetic film.
[0048]
In order to achieve the second object, a magnetic storage device of the present invention comprises any one of the above magnetic recording media, a drive unit that drives the magnetic recording medium, a recording unit, and a reproducing unit, and Magnetic head composed of a magnetoresistive effect type magnetic head, means for moving the magnetic head relative to the magnetic recording medium, recording for performing signal input to the magnetic head and reproduction of output signal from the magnetic head Reproduction signal processing means.
[0049]
In this magnetic storage device, the magnetoresistive sensor portion of the magnetoresistive head is formed between two shield layers made of a soft magnetic material separated from each other by a distance of 0.3 μm or less. preferable.
[0050]
The two shield layers made of soft magnetic material are preferably separated by a distance of 0.3 μm or less, and are separated by a distance exceeding 0.3 μm, and the magnetoresistive sensor part of the magnetoresistive effect type magnetic head between them This is because the reproduction output value becomes small and the output resolution is difficult to obtain. In addition, this distance is preferably 0.1 μm or more from the viewpoint of ease of work.
[0051]
In addition, the magnetoresistive head has a plurality of conductive magnetic layers that cause a large change in resistance when their magnetization directions are relatively changed by an external magnetic field, and a conductive layer disposed between the conductive magnetic layers. Even when the magnetoresistive sensor includes a nonmagnetic layer, the sensitivity of the reproducing head is improved. Therefore, the value of the product Br × t of the information recording layer thickness t and the residual magnetic flux density Br of the magnetic recording medium is set to the above value. It is preferable to set it as the range.
[0052]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional structure diagram of an embodiment of a magnetic recording medium of the present invention.
An alloy containing at least one oxide of at least one element of the first element group such as Ti and Zr, a second element (for example, Cr), and nitrogen (on the nonmagnetic nonmetallic substrate 1) For example, a nonmagnetic intermediate layer 2 ′ made of a Cr alloy) is provided, and a metal underlayer 2 and an information recording layer 3 are laminated on the nonmagnetic intermediate layer 2 ′, and a protective film 4 and a lubricating film 5 are formed. Has been.
[0053]
The non-magnetic non-metallic substrate 1 is made of ceramics, glass, chemically tempered glass, crystallized glass, titanium, silicon, carbon, or glass glazing, as well as Ni—P plated on an Al—Mg alloy disc. A substrate or the like is used. When an Al—Mg alloy is used as the substrate, Ni—P, Ni—WP, or the like is used after plating.
The non-magnetic non-metallic substrate 1 may have an outer diameter of 2.5 inches, 3 inches, 3.5 inches, 1.8 inches, 1.3 inches, or the like.
[0054]
The oxygen concentration in the thickness direction of the nonmagnetic intermediate layer 2 ′ may be configured to decrease continuously or stepwise in the direction of the metal underlayer or a combination of both. At this time, the metal underlayer side of the nonmagnetic intermediate layer 2 ′ may have a portion not containing oxygen.
[0055]
The nonmagnetic intermediate layer having such a structure is used for the following reason. The metal underlayer 2 is present on the nonmagnetic intermediate layer 2 ′ (on the side opposite to the substrate). Now, the nonmagnetic intermediate layer 2 ′ is made of Cr—ZrO. ₂ -N, and when the metal underlayer 2 is made of a Cr-Zr alloy, the oxide (ZrO ₂ ) May move to the metal underlayer and form an oxide with Zr constituting the alloy. For this reason, the properties of the metal underlayer change, and for example, a body-centered cubic structure may not be adopted. At this time, if Cr—Zr—N is formed as a second nonmagnetic intermediate layer on the nonmagnetic intermediate layer 2 ′, and oxygen is moved up to the second nonmagnetic intermediate layer, The metal underlayer can maintain desired properties. By such a manufacturing method, a structure is obtained in which the oxygen concentration in the thickness direction of the nonmagnetic intermediate layer is high on the nonmetal substrate side and decreases toward the metal underlayer.
[0056]
The oxygen concentration in the thickness direction of the nonmagnetic intermediate layer does not have to change. For example, the nonmagnetic intermediate layer 2 ′ is made of Cr—ZrO. ₂ When -N is used and the metal underlayer 2 is made of a Cr-Ti alloy, oxygen hardly moves due to the difference in oxygen affinity between Zr and Ti.
[0057]
The metal underlayer 2 is preferably made of Cr or a Cr alloy and has a body-centered cubic structure (bcc structure). The metal underlayer 2 may contain at least one element selected from Ti, Zr, Hf, V, Nb, Ta, Mo, W, Si, Al and the like.
[0058]
As the composition of the information recording layer 3, the Co-Cr-Pt system represented by Co-19 atomic% Cr-6 atomic% Pt, Co-20 atomic% Cr-8 atomic% Pt, etc., Co-Cr-Pt- Ta, Co—Cr—Ta, Co—Ni—Cr, Co—Ni—Cr—Pt, Co—Sm, Co—Ni—Pt, Co—Ni—P, Co—Cr—W, Co—Cr—Si, etc. In particular, a Co-based alloy generally used for in-plane magnetic recording can be used even if it contains an oxide.
As the protective film 4, carbon, boron, SiO ₂ Etc. are used.
[0059]
A magnetic recording medium is expected to have a mass production effect when manufactured using a physical vapor deposition method, particularly a DC sputtering method. As an example of the present sputtering method, the method described in Journal of Applied Physics, Vol. 75, No. 10, May 15, 1994, page 6138 (J. Appl. Phys., Vol. 75, p. 6138 (1994)). It has been known. The same effect can be obtained by using RF sputtering or ion beam sputtering.
[0060]
For example, in a single wafer sputtering apparatus in which each film is formed in a separate film forming chamber, each film is sequentially fed one by one with a constant tact time of 23 seconds, and each film is formed by a DC magnetron sputtering method. Deposition conditions are main vacuum chamber back pressure: 5 × 10 ^-8 Below Torr, substrate heating temperature: 100 to 300 ° C., Ar gas pressure: 5 to 30 mTorr, input power: 1 to 4 kW for a target size of 6 inches. The formation of the nonmagnetic intermediate layer 2 ′ is performed by the oxide of the first element (for example, ZrO ₂ ) And a second element (for example, Cr) is obtained by reactive sputtering in an atmosphere containing nitrogen. Alternatively, a Cr-15 at% V-5 at% Zr alloy with 10 mol% ZrO ₂ It can manufacture by the same method using the target which added.
[0061]
Since the nonmagnetic intermediate layer is formed at a temperature ranging from room temperature to 150 ° C., and then the substrate is heated to a temperature exceeding 150 ° C. and below 400 ° C., the coercive force is improved. preferable. Further, it is preferable that the substrate temperature in forming the information recording layer is 200 ° C. or more and 400 ° C. or less because the segregation of Cr in the information recording layer is promoted and Hc is improved.
[0062]
<Example 1>
After cleaning a chemically strengthened glass substrate having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.635 mm, a vacuum state was formed without heating in a DC in-line sputtering apparatus, and nitrogen was added by 10% (volume%, the same applies hereinafter). Cr-10 mol% ZrO at a discharge gas pressure of 20 mTorr in Ar gas ₂ By sputtering the target, a nonmagnetic intermediate layer 2 ′ of Cr alloy containing Zr and nitrogen simultaneously oxidized and having a thickness of 25 nm was formed. Then, it heated so that a substrate actual temperature might be set to 250 degreeC.
[0063]
In a continuous process after forming the nonmagnetic intermediate layer, without adding nitrogen, the metal underlayer 2 made of a Cr—Ti alloy is formed to a thickness of 30 nm, and information recording made of Co-20 at% Cr-8 at% Pt. Layer 3 was formed to a thickness of 15.4 nm. The non-magnetic intermediate layer 2 ′ made of a Cr alloy containing oxide, the metal underlayer 2, the information recording layer 3 and the like can be easily controlled in an atmosphere that does not contain nitrogen easily by forming a thin film in an independent vacuum chamber. It becomes possible.
Further, after forming the protective film 4 mainly composed of carbon so as to have a thickness of substantially 13 nm, the lubricating film 5 was formed with a liquid lubricant.
[0064]
According to Auger analysis, it was confirmed that the nonmagnetic intermediate layer 2 ′ of the Cr alloy contained approximately 31 atomic% of nitrogen with respect to the total of Cr and N. Here, the Auger signal intensity (dN (E) / dE) was calculated using a signal of 379 eV for nitrogen and 577 eV for Cr.
[0065]
Note that Fe and Y contained in the alloy target ₂ O _Three Even if a constituent element unavoidable for target formation is included, the present invention is not affected at all. Elemental iron mixed in the target is in a trace amount that is mixed into the target during grinding. On the other hand, Y ₂ O _Three Is ZrO ₂ Since a large volume change accompanying the phase transformation that occurs during sintering can be suppressed, a certain amount is preferably contained.
[0066]
The magnetic conversion characteristics of the magnetic recording medium were measured with a magnetic flying height of 75 nm. The gap length of the writing element was 0.6 μm, and the shield gap length of the reading element was 0.25 μm. Sense current density is 30MA / cm ² It was. The outputs at 172 kFCI (41.03 MHz) and 180 kFCI (42.94 MHz) were 22.6% and 18.7%, respectively, with respect to the isolated reproduction wave output at 5 kFCI (1.19 MHz). Also, the ratio SLF between the output of the isolated reproduction wave (SLF) and the medium noise (Nd) of 2F _0p / Nd was 34.7 and 35.6, respectively. That is, in the logarithmic display shown by the following equation, SLF / Nd was 30.8 dB and 31.0 dB, respectively.
SLF / Nd = 20 log [E (5kFCI) pp / 2Nd]
In the above equation, the bandwidth for Nd calculation is 0.5 MHz to 62 MHz and 0.5 MHz to 65 MHz for 172 kFCI and 180 kFCI, respectively.
[0067]
The crystal orientation of the magnetic recording medium was evaluated using an X-ray diffractometer. CuKα monochromatic with a monochromator for the X-ray source ₁ A line was used. As a result, only 110 diffraction peaks considered to be attributable to the nonmagnetic intermediate layer and the metal underlayer were observed, and 200 diffraction peaks were not observed. Further, 10 · 0 and 10 · 1 were recognized as diffraction peaks considered to be caused by the information recording layer, and the diffraction intensity was particularly high at 10 · 0.
[0068]
As described above, when the magnetic flying height is between 65 nm and 81 nm and the linear recording density is about 172 kFCI to 200 kFCI, this magnetic recording medium has a large ratio of the output of the isolated reproduction wave to these linear recording densities. became.
[0069]
In addition, ZrO used for the above target ₂ Instead of Ti, Hf, V, Nb, Ta, Mo, W, Si, and Al, the same result can be obtained when using one oxide or two or more oxides in the same mol%. It was.
[0070]
<Comparative example 1>
After cleaning the substrate in the same manner as described above, a vacuum state is formed without heating in a DC sputtering apparatus, and nitrogen is sputtered by sputtering a Cr target at a discharge gas pressure of 20 mTorr in Ar gas added with 10% nitrogen. A magnetic recording medium was formed by the same process as in Example 1 except that the nonmagnetic intermediate layer 2 ′ made of the contained Cr alloy was formed to a thickness of 25 nm, and the electromagnetic conversion characteristics were measured. That is, this magnetic recording medium uses ZrO as the sputtering target material for forming the nonmagnetic intermediate layer. ₂ It is changed to Cr not containing.
[0071]
As a result, the outputs at 172 kFCI and 180 kFCI were 21.3% and 17.9%, respectively, with respect to the output of the isolated reproduction wave at 5 kFCI. Also, the ratio of the output of the isolated reproduction wave and the medium noise of 2F SLF _0p / Nd was 32.9 and 32.2, respectively. That is, in the logarithmic display, SLF / Nd was 30.4 dB and 30.2 dB, respectively. From these results, it was found that the output resolution and SLF / Nd were lowered in this comparative example as compared to Example 1.
[0072]
<Comparative example 2>
After cleaning the substrate in the same manner as described above, a vacuum state is formed without heating in a DC sputtering apparatus, and sputtering is performed at a discharge gas pressure of 20 mTorr in Ar gas to which nitrogen is not added. A magnetic recording medium was formed in the same manner as in Example 1 except that the contained Cr alloy nonmagnetic intermediate layer 2 ′ was formed to a thickness of 25 nm. That is, this comparative example corresponds to the case where nitrogen is removed from the discharge gas when forming the nonmagnetic intermediate layer 2 ′ of the alloy mainly composed of Cr described in Example 1.
[0073]
As a result of measuring the electromagnetic conversion characteristics of the medium, the outputs at 172 kFCI and 180 kFCI were 19.3% and 16.2%, respectively, with respect to the output of the solitary reproduction wave at 5 kFCI. Also, the ratio of the output of the isolated reproduction wave and the medium noise of 2F SLF _0p / Nd was 22.5 and 21.9, respectively. That is, in the logarithmic display, SLF / Nd was 27.1 dB and 26.8 dB, respectively.
[0074]
From these results, compared with Example 1, in this comparative example, when the nonmagnetic intermediate layer 2 ′ made of an alloy containing Cr as a main component without containing nitrogen is formed, the output resolution and SLF / Nd are lowered. I understood.
[0075]
<Comparative Example 3>
In the same manner as in Comparative Example 2, no nitrogen was added during formation of the nonmagnetic intermediate layer 2 ′, and ZrO was added to the sputter target. ₂ A magnetic recording medium was formed in the same manner as in Example 1 except that the nonmagnetic intermediate layer 2 ′ was formed without adding. That is, in this comparative example, the nonmagnetic intermediate layer 2 ′ does not contain nitrogen, and ZrO ₂ Not included.
[0076]
As a result of measuring the electromagnetic conversion characteristics of the above medium, the outputs at 172 kFCI and 180 kFCI were 19.8% and 16.7% with respect to the output of the solitary reproduction wave at 5 kFCI, respectively. Also, the ratio of the output of the isolated reproduction wave and the medium noise of 2F SLF _0p / Nd was 28.1 and 27.5, respectively. That is, in logarithmic display, SLF / Nd was 29.0 dB and 28.8 dB, respectively.
Table 1 shows the magnetic characteristics of these magnetic recording media.
[0077]
[Table 1]

[0078]
Brt, S *, S, and vIs shown in Table 1 indicate the product of residual magnetization and information recording layer thickness, coercivity squareness ratio, squareness ratio, and activation magnetic moment, respectively. For example, Journal of Magnetics and Magnetic Materials, Vol. 152 (1996), pages 411 to 416 (Journal of Magnetics and Magnetic Materials, vol. 152 (1996) pp. 411 to 416). Or the method described in TECHNICAL REPORT OF IEICE MR96-4 (1996-06) was used. As a result of investigating the relationship between this vIs and noise at high linear recording density, it was found that the medium noise decreased qualitatively as vIs decreased, and there was a strong correlation between the two.
[0079]
The ratio of output to medium noise S / Nd at high linear recording density (2F) was defined by the following equation.
S / Nd = 20 log [E (2F) pp / 2Nd]
The relationship between S / Nd and output resolution measured at 172 kFCI and 180 kFCI shows that the S / Nd and output resolution of the magnetic recording medium shown in Example 1 is higher than that of Comparative Examples 1 and 2 at any linear recording density. It was.
[0080]
In relation to the noise and vIs at 172 kFCI, the Nd of the magnetic recording medium shown in Comparative Example 1 was lower than the Nd of the magnetic recording medium shown in Example 1, but the output at 172 kFCI was compared with that in Example 1. Since S / Nd was larger than that in Example 1, the magnetic recording medium shown in Example 1 had the highest S / Nd.
These results are shown in FIGS. 2a to 7b.
[0081]
<Example 2>
For these magnetic recording media, the frequency was changed using the same head, and the electromagnetic conversion characteristics at 200 kFCI were evaluated. As a result, although the output resolution at 200 kFCI is smaller than the value at 180 kFCI, the output resolution Re, SLF / Nd, and S / Nd of the magnetic recording medium shown in Example 1 are larger than those of the magnetic recording medium described in the comparative example. It was.
[0082]
<Example 3>
For these magnetic recording media, the flying height hm of the head was changed by changing the rotational speed of the magnetic recording medium using the same head, and the electromagnetic conversion characteristics at 172 kFCI were evaluated. As a result, even when hm = 56 nm, 65 nm, and 81 nm, the output resolution Re, SLF / Nd, and S / Nd of the magnetic recording medium shown in Example 1 were larger than those of the magnetic recording medium described in the comparative example.
[0083]
<Example 4>
Magnetic recording media were formed in the same manner as described in Example 1 except that the discharge gas pressure was kept constant at 20 mTorr and the nitrogen concentration contained in Ar was 3% or 5%. Was measured. The result is shown in FIG. Compared to the case of Comparative Example 2 in which the nonmagnetic intermediate layer was formed without adding nitrogen, the vIs value was small when the nitrogen addition concentration was 3 to 5%. Furthermore, when the nitrogen addition concentration was 10%, the vIs value was further smaller than when the nitrogen addition concentration was 3 to 5%. Thus, the vIs value of the medium formed by adding nitrogen becomes small. When the nitrogen addition concentration is 3% and 10%, the nonmagnetic intermediate layer contains about 19 atomic% and about 31 atomic% of nitrogen with respect to Cr, respectively.
[0084]
In addition, excellent recording / reproducing characteristics having the same tendency as described above were obtained even with a prototype disk in which the film thickness of the nonmagnetic intermediate layer was changed from 10 nm to 100 nm.
[0085]
<Example 5>
As in Example 1, a Cr alloy nonmagnetic intermediate layer containing both preferentially oxidized Zr and nitrogen is formed to a thickness of 25 nm by sputtering in Ar gas to which nitrogen is added at a discharge gas pressure of 20 mTorr. did. Next, a second nonmagnetic intermediate layer made of a Cr alloy containing nitrogen is formed by sputtering a Cr target at a discharge gas pressure of 20 mTorr in an Ar gas added with 10% nitrogen in the same manner. A magnetic recording medium was formed in the same manner as in Example 1.
[0086]
Since the substrate is heated to 250 ° C. after the second nonmagnetic intermediate layer is formed, the oxygen amount ranges from the substrate side of the nonmagnetic intermediate layer to the metal underlayer side of the second nonmagnetic intermediate layer. There was a tendency to decrease. Depending on the material and conditions of the substrate, oxygen in the substrate may move to the nonmagnetic intermediate layer.
[0087]
The ratio SLF / Nd of the output at 172 kFCI (41.03 MHz) and 180 kFCI (42.94 MHz) of this magnetic recording medium and the output of the solitary reproduction wave (SLF) and the medium noise (Nd) of 2F are both Comparative Example 1, It was better than 2 and 3.
[0088]
<Example 6>
FIG. 9 shows a schematic perspective view of the magnetic head used for the measurement. A lower shield 10 made of a Co-based amorphous alloy is provided on the substrate, and then a first spacer 20 made of alumina is formed. After forming the MR element portion 100, a hard bias magnetic domain control film 60 was formed, and an electrode 70 was formed. Then, after the second spacer 30 made of alumina is formed again, a permalloy upper shield 90, a light gap portion 40 made of alumina, an insulator 130 made of resist, a plating coil 120, and an upper core 110 made of permalloy are formed by sputtering. The magnetic head 204 was formed by cutting and assembly.
[0089]
Next, a schematic perspective view of a magnetic memory device using this magnetic head is shown in FIG. This magnetic storage device includes a magnetic recording medium 203, a drive unit 202 that drives the magnetic recording medium 203 in the recording direction, a magnetic head 204 including a recording unit and a reproducing unit, and a magnetic head 204 that moves relative to the magnetic recording medium 203. And a recording / reproduction signal processing circuit 201 for performing signal input to the magnetic head and reproduction of an output signal from the magnetic head. In this magnetic storage device, the reproducing part of the magnetic head is composed of a magnetoresistive effect type magnetic head, and the magnetoresistive sensor part is between two shield layers made of a soft magnetic material separated from each other by a distance of 0.25 μm. And the sense current density is 22 MA / cm. ² The magnetic flying height, that is, the flying height from the surface of the information recording layer of the magnetic recording medium to the gap sensor surface of the reading element was set to 72 nm, and the electromagnetic conversion characteristics of the magnetic recording medium were measured at 172 kFCI. The result was qualitatively similar to the previous result.
[0090]
<Example 7>
Instead of the magnetoresistive effect type magnetic head used in Embodiment 6, the magnetoresistive sensor portion is formed between two shield layers made of a soft magnetic material separated from each other by 0.2 μm. The electromagnetic conversion characteristics of the magnetic recording medium were evaluated in the same manner as in Example 5 except that the magnetic head was used. As a result, the ratio of the output of 5 kFCI isolated reproduction group to the output of 172 kFCI uses a head formed between two shield layers made of a soft magnetic material in which magnetoresistive sensor parts are separated from each other by 0.25 μm. Compared with the case where the head was used, the output resolution was larger when the head formed between the two shield layers made of the soft magnetic material separated from each other by 0.2 μm was used.
[0091]
<Example 8>
Instead of the magnetoresistive effect type magnetic head used in Example 6, a plurality of conductive magnetic layers that cause a large change in resistance due to relative changes in the magnetization directions of each other by an external magnetic field; and A magnetic storage device was configured with the same configuration as that shown in FIG. 10 except that a magnetic head constituted by a magnetoresistive sensor including a conductive nonmagnetic layer disposed therebetween was used. The Br × t of the magnetic recording medium used for the measurement was 1.5, 2, 4, 6.2, 8.5, 10 nWb / m (15, 20, 40, 62, 85, 100 gauss microns). When Br × t is 1.5 nWb / m, the coercive force of the magnetic recording medium is drastically reduced, and it is difficult to obtain a practically preferable coercive force. If it exceeds 10 nWb / m, the output of 2F is large. It became clear that the output resolution was unfavorable.
[0092]
<Example 9>
Dirt such as abrasives adhering to a glass disk substrate having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.635 mm was washed and dried. After loading this substrate into the substrate preparation chamber of a single-wafer DC magnetron sputtering apparatus and evacuating it to a vacuum, the substrate is non-magnetic intermediate layer forming chamber, heating chamber, metal underlayer forming chamber, magnetic film forming chamber, protective film forming The degree of vacuum is 5 × 10 in the order of chamber and take-out chamber ^-8 The film was conveyed through the main exhaust tank below Torr, and each film was formed in each chamber. The cross-sectional structure of the manufactured magnetic disk is the same as that shown in FIG.
[0093]
First, after cleaning the substrate, a vacuum state is formed without heating in a DC in-line sputtering apparatus, and in Ar gas to which 10% of nitrogen is added, a discharge gas pressure of 2.66 Pa (20 mTorr) and Cr-10 mol% ZrO. ₂ A nonmagnetic intermediate layer 2 ′ of Cr alloy containing nitrogen simultaneously containing Zr that was oxidized preferentially by sputtering the target and a thickness of 25 nm was formed.
[0094]
In a continuous process after the formation of the nonmagnetic intermediate layer, Cr-20 at. The metal underlayer 2 made of a Ti alloy is 30 nm thick and Co-21.5 at. % Cr-9 at. The information recording layer 3 made of% Pt was formed to a thickness of 18 nm. The nonmagnetic intermediate layer 2 ′ containing the oxide, the metal underlayer 2, the information recording layer 3 and the like can be easily controlled in an atmosphere free from nitrogen by forming a thin film in an independent vacuum chamber.
[0095]
Further, a power of 1.5 kW was applied to the target under an argon pressure of 1.33 Pa on the information recording layer 3 to form a protective film 4 mainly composed of carbon having a thickness of 9 nm. Then, a lubricating film 5 such as adsorptive perfluoroalkyl polyether was formed on the protective film 4 to obtain a 2.5 inch magnetic disk.
[0096]
By Auger analysis, it was confirmed that the nonmagnetic intermediate layer 2 ′ contained approximately 16 atomic% of nitrogen with respect to the total of Cr and N. The vIs of this magnetic disk is 1.4 × 10 ^{-twenty four} Wb · m and Hc were 178 kA / m, and Hr was 185 kA / m.
Note that Fe and Y contained in the alloy target ₂ O _Three Even if constituent elements unavoidable for target formation are included, the present invention is not affected at all.
[0097]
The magnetic conversion characteristics of the magnetic disk were measured with a magnetic flying height of 56 nm. For evaluation of recording / reproducing characteristics, a magnetic head having a gap length of 0.3 μm, a track width of 1.5 μm, a thin film type head having 17 windings, a shield interval of 0.2 μm, and a track width of 1 μm for reproduction Using a recording / reproducing separated type head having a GMR head, the sense current density is 40 MA / cm ² And the value of S / Nd at a linear recording density of 300 kFCI was determined.
[0098]
The output at 5.9 kFC / mm (150 kFCI) was 45% with respect to the output of the solitary reproduction wave. Further, the ratio SLF / Nd between the output (SLF) of a solitary reproduction wave at 197 FC / mm (5 kFCI) and the medium noise (Nd) at 11.8 kFC / mm (300 kFCI) represented by the following formula was 27.2 dB. In the following equation, the bandwidth at the time of Nd calculation was set to 0.5 MHz to 75 MHz.
SLF / Nd = 20 log [E (5kFCI) pp / 2Nd]
Also, an 8 mm square sample was cut out from this magnetic disk, and a KV / kT value representing the thermal stability of the recorded state was obtained by the method described in TECHNICAL REPORT OF IEICE MR96-4 (1996-06). It was measured. As a result, this value was 103 at room temperature.
[0099]
Regarding the reproduction output of this magnetic disk, after recording a signal from 197 FC / mm (5 kFCI) to 11.8 kFC / mm (300 kFCI) for 1 minute after recording, the reproduction output at that time was measured 25 times and left at 24 ° C. for 105 hours. Then, the change with time of the reproduction output was measured. The reproduction output signal at 197 FC / mm (5 kFCI) was measured with a digital oscilloscope (Tektronix TDS544A), and the reproduction signal output at 11.8 kFC / mm (300 kFCI) was measured with a spectrum analyzer HP 8560E manufactured by HP. No reduction in reproduction output was observed at any linear recording density, and no reduction in output was observed with a measurement accuracy of less than 1%.
[0100]
Further, a magnetic disk using Cr-10 atomic% Mo, Cr-20 atomic% V, Cr-20 atomic% Nb instead of Cr-Ti as the metal underlayer in this example was manufactured, and its characteristics were evaluated. did.
[0101]
As a result, the value of vIs is 1 × 10 ^{-twenty four} From Wb · m 1.4 × 10 ^{-twenty four} Wb · m, and the KV / kT value was 100 to 140. When Hr was 160 kA / m or higher and 190 kA / m, OW was 40 dB or higher with a head of Tww = 1.5 μm. On the other hand, when Hr exceeded 190 kA / m, OW was not 40 dB.
[0102]
<Example 10>
Cr-10 mol% ZrO described in Example 9 ₂ Instead of the target, (Cr-15 at.% Nb) -10 mol% ZrO ₂ Target, (Cr-15 at.% V) -10 mol% ZrO ₂ Target, V to (V ₂ O _Five -MoO _Three -WO _Three ), Nb-10 mol% SiO target added 15% by weight ₂ Target or Cr-5 mol% ZrO ₂ -5 mol% Al ₂ O _Three Using the target as a nonmagnetic intermediate layer, the target for forming the information recording layer was Co-21.5 at% Cr-8 at% Pt, Co-23 at. % Cr-8 at. % Pt or Co-23 at. % Cr-10 at. A medium was formed in the same manner as in Example 9 except that% Pt was used.
[0103]
The value of vIs of this magnetic disk is 0.6 × 10 ^{-twenty four} 1.4 × 10 from Wb · m ^{-twenty four} The value of KV / kT, which indicates Wb · m and indicates the thermal stability of the recording state, was a value greater than 100 and less than 150. In either case, the medium noise was smaller than 7 μVrms, the OW was 30 dB or more, and no output reduction was observed. When Hr was 190 kA / m or less and KV / kT was 130 or less, OW was 40 dB or more.
[0104]
<Comparative example 4>
After cleaning the substrate in the same manner as in Example 9, a vacuum state was formed without heating in the DC sputtering apparatus, and the discharge gas pressure was 2.66 Pa (20 mTorr) in Ar gas with 10% nitrogen added. A magnetic recording medium was formed by the same process as in Example 9 except that the nonmagnetic intermediate layer 2 ′ containing nitrogen was formed to a thickness of 25 nm by sputtering the target, and the electromagnetic conversion characteristics were measured. That is, this magnetic recording medium uses ZrO as the sputtering target material for forming the nonmagnetic intermediate layer. ₂ It is changed to Cr not containing.
[0105]
As a result, vIs is 1.5 × 10 ^{-twenty four} Wb · m, and the output at 5.9 kFC / mm (150 kFCI) was 42% with respect to the output of the solitary reproduction wave. The ratio SLF / Nd between the output of the isolated reproduction wave (SLF) at 197 FC / mm (5 kFCI) and the medium noise (Nd) at 11.8 kFC / mm (300 kFCI) represented by the above formula was 26.0 dB.
[0106]
From these results, it became clear that the output resolution and SLF / Nd were lowered in this comparative example as compared with Example 9.
An 8 mm square sample was cut out from the magnetic recording medium, and the KV / kT value was measured. As a result, this value was 101.8 at room temperature.
[0107]
<Comparative Example 5>
After cleaning the substrate in the same manner as in Example 9, a vacuum state was formed without heating in the DC sputtering apparatus, and the target was sputtered at a discharge gas pressure of 2.66 Pa (20 mTorr) in Ar gas to which nitrogen was not added. Thus, a magnetic recording medium was formed by the same process as in Example 9 except that the nonmagnetic intermediate layer 2 ′ made of Cr alloy containing Zr containing oxidized predominantly was formed to a thickness of 25 nm. Conversion characteristics were measured. That is, this magnetic recording medium corresponds to the case where nitrogen is removed from the discharge gas when forming the nonmagnetic intermediate layer containing Cr as a main component and containing oxide as described in Example 9.
[0108]
As a result, vIs is 1.8 × 10. ^{-twenty four} Wb · m, and the output at 5.9 kFC / mm (150 kFCI) was 39% with respect to the output of the solitary reproduction wave. The ratio SLF / Nd between the output of the isolated reproduction wave (SLF) at 197 FC / mm (5 kFCI) and the medium noise (Nd) at 11.8 kFC / mm (300 kFCI) represented by the above formula was 23.1 dB.
[0109]
From these results, it was found that both the output resolution and the SLF / Nd were lowered in this comparative example as compared with Example 9.
An 8 mm square sample was cut out from the magnetic recording medium, and the KV / kT value was measured. As a result, this value was 120 at room temperature.
[0110]
<Comparative Example 6>
After cleaning the substrate in the same manner as in Example 9, a vacuum state was formed without heating in the DC sputtering apparatus, and the target was sputtered at a discharge gas pressure of 2.66 Pa (20 mTorr) in Ar gas to which nitrogen was not added. As a result, a nonmagnetic intermediate layer 2 ′ made of a Cr alloy containing Zr having a surface oxidized with a thickness of 25 nm is formed, and the composition of the information recording layer is Co-23 at. % Cr-7 at. A magnetic disk was formed by the same process as in Example 9 except that it was changed to% Pt, and the electromagnetic conversion characteristics were measured by setting the magnetic flying height to 56 nm and 62 nm.
[0111]
As a result, vIs is 1.15 × 10. ^{-twenty four} The ratio SLF / Nd between the output (SLF) of the solitary reproduction wave at 197 FC / mm (5 kFCI) and the medium noise (Nd) at 10.2 kFC / mm (260 kFCI) shown in the above formula is Wb · m. They were 30.97 and 30.09 dB with respect to the flying height, respectively.
[0112]
An 8 mm square sample was cut out from the magnetic disk, and a KV / kT value representing the thermal stability of the recorded state was measured. As a result, this value was 100 at room temperature. After recording a signal of 197 FC / mm (5 kFCI) to 10.2 kFC / mm (260 kFCI) on this magnetic disk, the time change of the reproduction output at these signal recording densities was observed. As a result, when the magnetic flying height was 62 nm after 4 days, the reproduction output of 197 FC / mm (5 kFCI) decreased by about 4% as shown in FIG. It was also revealed that the reproduction output at 10.2 kFC / mm (260 kFCI) decreased by about 8% when the magnetic flying height was changed from 56 to 62 nm.
[0113]
The magnetostatic characteristics (coercive force Hc, squareness ratio S *) of the magnetic disk thus formed were evaluated by the following methods. The magnetostatic characteristics are obtained by cutting the magnetic disk into a substantially square shape of 8 mm × 8 mm from a radius of 20 mm, preparing a sample by scraping off one side of the magnetic film, and using a vibrating sample magnetometer (VSM). The magnetostatic characteristics in the in-plane direction were determined with the maximum applied magnetic field being 13 kOe. The magnetic properties of this medium are as follows. The coercive force was 160 kA / m (2.0 kOe), Brt = 6.79 nWb / m, S * = 0.59, and S = 0.64.
[0114]
<Example 11>
After the substrate was cleaned in the same manner as in Example 9, a vacuum state was formed without heating in the DC sputtering apparatus, and the target was sputtered at a discharge gas pressure of 2.66 Pa (20 mTorr) in Ar gas added with nitrogen. As a result, a Cr alloy intermediate layer A2 ′ containing Zr whose surface was oxidized preferentially was formed to a thickness of 25 nm, and the composition of the information recording layer was changed to Co-23 at. % Cr-7 at. A magnetic disk was formed by the same process as in Example 9 except that it was changed to% Pt, and the electromagnetic conversion characteristics were measured by setting the magnetic flying height to 56 nm and 62 nm.
[0115]
As a result, vIs is 1.2 × 10 ^{-twenty four} It is Wb · m, and the ratio SLF / Nd between the output of the solitary regenerative wave (SLF) at 197 FC / mm (5 kFCI) and the medium noise (Nd) at 10.2 kFC / mm (260 kFCI) shown in the above formula The amounts were 31.19 and 29.87 dB, respectively.
[0116]
An 8 mm square sample was cut out from the magnetic disk, and a KV / kT value representing the thermal stability of the recorded state was measured. As a result, this value was 110.4 at room temperature.
[0117]
After recording a signal of 197 FC / mm (5 kFCI) to 10.2 kFC / mm (260 kFCI) on this magnetic disk, the time change of the reproduction output at these signal recording densities was observed. As a result, when the magnetic flying height is 62 nm after 4 days, reproduction output at 197 FC / mm (5 kFCI) and 10.2 kFC / mm (260 kFCI) is recognized when the magnetic flying height is 56 to 62 nm. It became clear that it was not possible.
[0118]
The magnetostatic characteristics of the magnetic disk thus formed are as follows. The coercive force was 176 kA / m (2.2 kOe), Brt = 7.21 nWb / m, S * = 0.65, and S = 0.70.
[0119]
<Example 12>
FIG. 12 shows an X-ray diffraction curve of a medium experimentally produced by changing the material of the nonmagnetic intermediate layer. The measurement is performed by an X-ray diffractometer RINT manufactured by Rigaku Corporation. A rotating copper cathode was used, the current was 100 to 160 mA, and the acceleration voltage was 50 kV. The sampling width was 0.02 degrees, the scanning speed was 2 degrees / minute, the diverging slit was 1 degree, the scattering slit was 1 degree, and the light receiving slit was 0.3 mm. A monochromator was used, and the monochromator light receiving slit was 0.45 mm. The scan angle range was 30 ° to 90 ° at 2θ, and θ-2θ scan was performed.
[0120]
The sample configuration used for the measurement was C protective film / Co—Cr—Pt information recording layer (thickness 15 nm) / Cr—Ti metal underlayer (thickness 30 nm) / Cr— (ZrO) from the surface. ₂ ) Nonmagnetic intermediate layer (thickness 25 nm) / chemically tempered glass substrate.
[0121]
From the low-angle side of the diffraction curve, (1) the 10.0 diffraction peak of the (Co-Cr-Pt) information recording layer having the hcp structure, and (2) 110 diffraction of the metal base film having the (cc-Ti) bcc structure. A peak, (3) a 110 diffraction peak of the nonmagnetic intermediate layer having the same bcc structure, and (4) a 10.1 diffraction peak of the information recording layer having the hcp structure (Co—Cr—Pt) were observed. Of these diffraction peaks, the diffraction intensity due to the (Cr—Ti) metal base film of (2) is the highest. Diffraction peaks other than (1) to (4) were not found in the scanned range (30 to 90 degrees). Since a 10.0 diffraction peak of the (Co—Cr—Pt) information recording layer having the hcp structure was observed, there is a possibility that 211 oriented microcrystals exist in the metal underlayer.
[0122]
The diffraction curve indicated by A in the figure is a comparative example, and the nonmagnetic intermediate layer is made of Cr containing no oxide, and Ar (N) at a low gas pressure (1.06 Pa). ₂ The diffraction curve shown by B in the figure is a comparative example, and the nonmagnetic intermediate layer is made of Cr containing no oxide and made of Ar (N) with a high gas pressure (2.66 Pa). ₂ Is not included)
The diffraction curve indicated by C in the figure is a comparative example, and when the non-magnetic intermediate layer is formed of Ar not containing an oxide and Ar added with 10% by volume of nitrogen at a high gas pressure (2.66 Pa),
The diffraction curve indicated by D in the figure is an example, and the nonmagnetic intermediate layer is represented by ZrO. ₂ In the case where Cr containing Cr is formed of Ar added with 10% by volume of nitrogen at a high gas pressure (2.66 Pa), the diffraction curve indicated by E in the figure is a comparative example, and the nonmagnetic intermediate layer is made of ZrO. ₂ Cr containing Ar (N) at high gas pressure (2.66 Pa) ₂ Is not included).
[0123]
When the nonmagnetic intermediate layer is formed at a low gas pressure (1.06 Pa) (A), the crystallinity is highest. When the nonmagnetic intermediate layer is formed of Ar at a high gas pressure (2.66 Pa), the diffraction intensity of the nonmagnetic intermediate layer and the metal underlayer is lower and the crystallinity is lower than that of (A). . Further, when 10% by volume of nitrogen was added to the discharge gas (C), the crystallinity was further lowered, and in particular, the diffraction intensity of the nonmagnetic intermediate layer was reduced.
[0124]
(Cr-ZrO ₂ ) When the nonmagnetic intermediate layer is formed of Ar at a high gas pressure (2.66 Pa) (E), compared to the nonmagnetic intermediate layer (B) of Cr containing no oxide, the nonmagnetic intermediate layer and the metal The diffraction intensity of the formation decreased and the crystallinity further decreased. Further, when 10% by volume of nitrogen was added to the discharge gas (D), the diffraction intensity of the metal underlayer decreased.
[0125]
Under any formation condition of the nonmagnetic intermediate layer, the 10 · 0 and 10 · 1 diffraction peaks of the information recording layer having the hcp structure are observed, and the orientation of Co10 · 0 decreases when the crystallinity of the nonmagnetic intermediate layer or the metal underlayer decreases. Increased slightly.
[0126]
From the above measurement results, a system in which an intermediate layer was formed only with Ar without adding nitrogen was selected as a system with relatively high crystallinity, and the crystallinity of the nonmagnetic intermediate layer was examined. The wavelength of the characteristic X-ray used for the measurement is λ, the half width of the diffraction curve is B [rad], and the angle of the diffraction peak for measuring the half width is 2θ. _B Then, the crystal grain size t of the intermediate layer can be preliminarily evaluated by the Scherrer formula shown below.
[0127]
t = 0.9λ · cos (2θ _B )
Cr and (Cr-ZrO) formed by changing Ar discharge gas pressure ₂ ) The 110 diffraction curve of the nonmagnetic intermediate layer is shown in FIG. As the discharge gas pressure increased, the 110 diffraction intensity of the non-magnetic intermediate layer containing only Cr decreased. (Cr-ZrO ₂ ) The 110 diffraction intensity of the non-magnetic intermediate layer is weaker than the 110 diffraction intensity of the non-magnetic intermediate layer of only Cr regardless of the discharge gas pressure. When the relationship between the lattice constant and the discharge gas pressure was determined from the 110 diffraction peak of the nonmagnetic intermediate layer, the lattice constant increased as the discharge gas pressure increased. Regardless of the discharge gas pressure, (Cr-ZrO ₂ ) The lattice constant of the nonmagnetic intermediate layer is slightly larger than the lattice constant of the nonmagnetic intermediate layer containing only Cr.
[0128]
Cr and (Cr-ZrO) formed by changing the discharge gas pressure ₂ FIG. 14 shows the relationship between the half width of the 110 diffraction peak of the nonmagnetic intermediate layer and the discharge gas pressure. The full width at half maximum of the 110 diffraction peak of the nonmagnetic intermediate layer increased as the discharge gas pressure increased. Regardless of the discharge gas pressure, (Cr-ZrO ₂ ) The half-value width of the 110 diffraction peak of the nonmagnetic intermediate layer is larger than the half-value width of the nonmagnetic intermediate layer containing only Cr. Corresponding to this trend (Cr-ZrO ₂ ) The crystal grain size of the nonmagnetic intermediate layer is expected to be about 4 to 8 nm, which is about half that of the nonmagnetic intermediate layer containing only Cr (FIG. 15). In the system to which nitrogen is added, the crystallinity is further lowered as shown in FIG. 12, and the crystal grains are considered to be finer.
[0129]
【The invention's effect】
As described above, the magnetic recording medium of the present invention showed high output resolution at a high linear recording density while improving the adhesive strength between the metal underlayer and the substrate, and the ratio of output to noise increased. Also, the magnetic storage device of the present invention was suitable for using such a magnetic recording medium.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a magnetic recording medium of the present invention.
FIG. 2 is a diagram showing a relationship between SLF / Nd measured by 172 kFCI and output resolution Re.
FIG. 3 is a diagram showing the relationship between SLF / Nd measured at 180 kFCI and output resolution Re.
FIG. 4 is a diagram showing the relationship between Nd and activation magnetic moment measured by 172 kFCI.
FIG. 5 is a graph showing the relationship between Nd and activation magnetic moment measured at 180 kFCI.
FIG. 6 is a diagram showing the relationship between S / Nd measured by 172 kFCI and output resolution Re.
FIG. 7 is a diagram showing the relationship between S / Nd measured at 180 kFCI and output resolution Re.
FIG. 8 is a graph showing the relationship between the activation magnetic moment and the nitrogen addition concentration.
FIG. 9 is a perspective view showing an example of a cross-sectional structure of a magnetic head.
FIG. 10 is a schematic diagram of a magnetic storage device of the present invention.
FIG. 11 is a diagram showing a change with time of output with respect to output immediately after recording.
FIG. 12 is a diagram showing an X-ray diffraction curve of a magnetic recording medium.
FIG. 13 shows an X-ray diffraction curve of a nonmagnetic intermediate layer.
FIG. 14 is a diagram showing a half-value width of a 110 diffraction peak.
FIG. 15 is a view showing the particle diameter obtained from the half-value width of a 110 diffraction peak.
[Explanation of symbols]
1 ... Non-metallic substrate
2 ... Metal underlayer
2 '... middle layer
3 ... Magnetic film
4 ... Protective film
5 ... Lubricating film
10 ... Bottom shield
20 ... 1st spacer
30 ... second spacer
40 ... Light gap
60 ... Magnetic domain control film
70 ... Electrode
90 ... Upper shield
100: MR element section
110 ... Upper core
120 ... Plating coil
130: Insulator
201: Recording / reproduction signal processing circuit
202 ... Driving unit
203 ... Magnetic recording medium
204 ... Magnetic head
205 ... Guide arm

Claims (6)

On a substrate, the non-magnetic intermediate layer, a magnetic recording medium in which information recording layer made of a magnetic film of a metal base layer and Co-base alloy are arranged in this order, the non-magnetic intermediate layer is an oxide of Zr, C r the magnetic recording medium characterized by containing at least 及 beauty nitrogen. In a magnetic recording medium in which an information recording layer including a nonmagnetic intermediate layer, a metal underlayer, and a Co-based alloy-based magnetic film is disposed in this order on a substrate, the nonmagnetic intermediate layer includes H f, V, Nb, Magnetic material comprising at least one oxide of at least one element selected from the first element group consisting of Ta, Mo, W, Si, Al and Y, a second element consisting of Cr, and nitrogen recoding media. 3. The magnetic recording medium according to claim 2, wherein the nonmagnetic intermediate layer further contains at least one element selected from the first element group or Zr . In a magnetic recording medium in which an information recording layer composed of a nonmagnetic intermediate layer, a metal underlayer, and a Co-based alloy-based magnetic film is disposed in this order on a substrate , the nonmagnetic intermediate layer includes Si oxide, Nb and the magnetic recording medium characterized that you at least contains nitrogen. In the magnetic recording medium as claimed in any one of 4, the oxide is a magnetic recording medium characterized by the presence segregated to the non-magnetic intermediate layer.   A magnetic recording medium; a drive unit for driving the magnetic recording medium; a magnetic head including a recording unit and a reproducing unit; means for moving the magnetic head relative to the magnetic recording medium; and a signal to the magnetic head A magnetic storage device having an input and a recording / reproducing signal processing means for reproducing an output signal from the magnetic head, wherein the reproducing unit of the magnetic head is composed of a magnetoresistive effect type magnetic head, and the magnetic recording medium A magnetic storage device according to claim 1, wherein the magnetic storage device is a magnetic recording medium according to claim 1.

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