JPH063768B2 - Perpendicular magnetic film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a perpendicular magnetization film having an easy axis of magnetization in a direction perpendicular to a film surface.

2. Description of the Related Art In recent years, a recording medium in which a reversed magnetic domain is recorded on a perpendicular magnetization film and the recorded information is read out by utilizing a magneto-optical effect or the like has been attracting attention. As such a recording medium, Japanese Patent Publication No. 57-20691 discloses a magnetic thin film recording medium provided with a Tb-Fe alloy whole film. The Tb-Fe alloy film exhibits vertical anisotropy and has a large coercive force and is suitable as a memory material, but the magneto-optical effect is insufficient, and
The magnetic properties such as vertical anisotropy and coercive force were further improved.

Object of the Invention It is an object of the present invention to provide a perpendicular magnetization film having excellent magnetic properties and magneto-optical properties.

Structure of the Invention The perpendicular magnetic film of the present invention has an ultrathin film having a thickness of 2.0 to 50 Å composed of at least one rare earth metal selected from Gd, Tb and Dy, and at least selected from Fe, Co, Ni, Cr and Cu. The present invention is characterized in that at least two layers of at least the whole are alternately laminated with an ultrathin film having a thickness of 2.5 to 50Å made of one kind of transition metal.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view schematically showing a structural example in which the perpendicularly magnetized film of the present invention is applied as a magneto-optical recording medium or a perpendicular magnetic recording medium. A transition metal film 13 and a rare earth metal film are formed on a substrate 11. 15 are stacked in sequence. in this way,
In the present invention, alternately stacking includes a case where each of the transition metal film and the rare earth metal film has one layer, and is composed of two layers in total.

The rare earth metal film 15 is formed of Gd (gadolinium), Tb (terbium) or Dy (dysprosium), and these are used alone or in combination. Rare earth metal film
The thickness of 15 is 2.0 to 50Å, preferably 2.0 to 20Å. If this film thickness is less than 2Å, the magnetic properties and magneto-optical properties do not change and show almost constant values, and if it exceeds 50Å, the magnetic properties and magneto-optical properties do not exhibit perpendicular magnetic anisotropy.

The transition metal film 13 is made of Fe (iron), Co (cobalt), Ni.
It is formed of (nickel), Cr (chrome) or Cu (copper), and these are used alone or in combination. The thickness of the transition metal film 13 is 2.5 to 50Å, preferably 2.5 to
It is 20Å. When the film thickness is less than 2.5Å, the magnetic properties and magneto-optical properties do not change and show almost constant values, and when it exceeds 50Å, the magnetic properties and magneto-optical properties do not exhibit perpendicular magnetic anisotropy.

As the substrate 11, for example, glass, plastic ceramic or the like is used.

FIG. 2 shows another configuration example, in which a plurality of layers of the transition metal film 13 and the rare earth metal film 15 are alternately laminated on the substrate 11. Each film is as described above. It is suitable that the transition metal film and the rare earth metal film are each laminated in an amount of 1 to 5000 layers (2 to 10,000 in total), and preferably 10 to 1000 layers each. Further, the thickness ratio of each layer of the rare earth metal film 15 and the transition metal film 13 can be arbitrarily set in the range of 1/5 to 2/1. If it deviates from this range, the film will not exhibit perpendicular magnetic anisotropy. Further, between the perpendicular magnetization film 17 and the substrate 11,
Alternatively, a protective film, a heat insulating film, a reflective film, and a high magnetic permeability material film can be provided on the upper surface of the perpendicular magnetization film 17.

To form the perpendicularly magnetized film of the present invention, the transition metal film and the rare earth metal film may be alternately provided on the substrate by a thin film forming method such as sputtering deposition or ion plating.

Effect According to the present invention, the saturation magnetization M is formed by forming the perpendicular magnetization film from the alternate laminated film of the transition metal film and the rare earth metal film.
s, coercive force Hc, and perpendicular anisotropy energy K⊥ are improved in magnetic performance, a perpendicular magnetization film with good reproduction performance is obtained, and the Kerr rotation angle θ _k is also increased. Therefore, information can be recorded and read out with high sensitivity. As described above, the perpendicular magnetic film of the present invention is useful as a magneto-optical recording medium and a perpendicular magnetic recording medium, and is applied to, for example, hard disks, floppy disks, document films and the like.

Example 1 A magnetron sputtering apparatus as shown in FIG. 3 was used. In this apparatus, two RF sputter electrodes 21 and 23 are arranged, and a transition metal target 25 and a rare earth metal target 27 are placed on the respective electrodes. By disposing the mask 29 on the target, a transition metal sputtering zone and a rare earth metal sputtering zone are formed, respectively. A substrate 33 is fixed to the substrate holder 31, and while rotating the substrate holder, sputtering causes the substrate 33 to alternately pass through both of the sputtering zones, thereby alternately laminating a transition metal film and a rare earth metal film. A film is formed. 22 and 24 are RF power supplies, and 26 is a gas introduction valve. Each RF electrode 2
By controlling the discharge power applied to 1, 23 and the rotation speed of the substrate, it is possible to control the film thickness of the transition metal film and the rare earth metal film and the film thickness ratio of both.

In the present embodiment, Fe is used as the transition metal, Tb is used as the rare earth metal, and sputtering is performed under the following conditions, and the ratio of the film thickness d _{1 of the} Tb film to the film thickness d ₂ of the Fe film is d ₁ :
By setting d ₂ = 1: 1.7 and changing the rotation speed of the substrate holder, alternate laminated films with various film thicknesses were formed, and a 1000 Å perpendicular magnetization film was formed as a whole.

Residual gas pressure: 1.0 × 10 ^-6 Torr Ar gas pressure: 5.0 × 10 ^-3 Torr Target material: Tb, Fe Discharge power: Tb; 125W Fe; 400W Sputtering time: 15min (1000Å) Base plate: Slide glass obtained The characteristics of the perpendicular magnetization film are shown in FIGS. 4 and 6 (curve Tb-Fe).

From Fig. 4, when d ₁ = 1.25 Å and d ₂ = 2.15 Å, a single layer structure of an alloy is shown instead of a laminated structure, but when it is thicker than that, Ms, Hc and K⊥ become large and the magnetic performance is You can see it improve.

Further, it can be seen from FIG. 6 that θ _k similarly increases and the magneto-optical performance also increases.

Example 2 Fe-Co is used as a transition metal, and T is used as a rare earth metal.
b, and the ratio of the film thickness d _{1 of the} Tb film to the film thickness d ₂ of the Fe—Co film was set to d ₁ : d ₂ = 1: 1.7, and sputtering was performed in the same manner as in Example 1 under the following conditions. Residual gas pressure: 1.0 × 10 ⁻⁶ Torr Ar gas pressure: 5.0 × 10 ⁻³ Torr Target material: Tb, Fe _0.85 Co _0.15 Discharge power: Tb; 125 W Fe _0.85 Co _0.15 ; 400 W Base plate: Slide glass The characteristics of the magnetized film are shown in FIGS. 5 and 6 (Tb-F).
e-Co curve).

Example 3 The manufacturing conditions are the same as in Examples 1 and 2, except that the rare earth metal (G
d, Dy, Tb) film pressure d ₁ and transition metal (Fe, C
o, Ni, Cr, Cu) film pressure d ₂ to the ratio d ₁ : d
₂ = 1: 1.7, and sputtering was performed under the following conditions.

Residual gas pressure: 1.0 × 10 ^-6 Torr Ar gas pressure: 5.0 × 10 ^-3 Torr Target material: Gd, Dy, Tb _0.50 Dy _0.50 Fe, Fe _0.85 Co _0.13 N
i _0.29 , Fe _0.85 Co _0.13 Cr _0.29 , Fe _0.85 Co _0.13 Cu _0.02 Discharge power; Gd; 100W Dy, Tb _0.50 Dy _0.50 ; 125W Fe, Fe _0.85 Co _0.13 Ni _0.02 , Fe _0.85 Co _0.13 Cr _0.02 , Fe _0.85 Co _0.13 Cu _0.02 : 400 W Sputtering time: 15 min (1000Å) Substrate: Slide glass The prepared film is Gd-Fe, Dy-Fe, Tb-Dy-
Fe, Tb-Fe-Co-Ni, Tb-Fe-Co-C
r, Tb-Fe-Co-Cu.

The result of the characteristics (Hc, Qk) of the obtained magnetic film is d ₁ = 0.5
The case of Å / d ₂ = 0.86Å and the range of the present invention d ₁ = 5Å
The results are summarized in Table 1 in the case of / d ₂ = 8.6Å.

From the results of Table 1, when d ₁ = 0.5Å / d ₂ = 0.86Å, each film has the same characteristics as in the case of the alloy single-layer structure, but d ₁
= 5Å / d ₂ = 8.6Å, and within the range of the present invention, Hc and Qk increased for each film, and the effect of the laminated structure occurred.

[Brief description of drawings]

FIG. 1 and FIG. 2 are cross-sectional views showing a configuration example of a magneto-optical recording medium or a perpendicular magnetic recording medium using the perpendicularly magnetized film of the present invention. FIG. 3 is a block diagram showing the magnetron sputtering apparatus used in the examples. 4 and 5 show the film thicknesses d ₁ and d ₂ and the saturation magnetization M.
It is a graph which shows the relationship with s, coercive force Hc, and perpendicular anisotropy energy K⊥. FIG. 6 is a graph showing the relationship between the film thicknesses d ₁ and d ₂ and the Kerr rotation angle θ _k . 11 ... Substrate, 13 ... Transition metal film 15 ... Rare earth metal film

Claims (1)

[Claims] 1. At least one selected from Gd, Tb and Dy
Ultra-thin film of 2.0 to 50 Å with rare earth metal
Perpendicular magnetization characterized in that at least two layers in total are alternately laminated with an ultrathin film having a thickness of 2.5 to 50 Å consisting of at least one transition metal selected from e, Co, Ni, Cr and Cu. film.