JP3880000B2 - High saturation magnetic flux density soft magnetic material - Google Patents

Description

  The present invention relates to a high saturation magnetic flux density soft magnetic material, and more particularly, to a high saturation magnetic flux density soft magnetic material that can be suitably used as a core material of a magnetic head that can be applied to a high coercive force recording medium.

  With the increase in capacity and speed of information recording, there has been remarkable progress in information storage devices in recent years. In particular, hard disks with large capacity, high speed, excellent reliability, and capable of rewriting information have built a solid position among information storage devices. However, as the recording density is increased due to the increase in capacity, the coercive force of the recording medium tends to increase, and the core material of the magnetic recording head for recording on such a high coercive recording medium is higher. There is a need for a soft magnetic film having a saturation magnetic flux density.

The soft magnetic film used for the magnetic head core material is first required to have a high saturation magnetic flux density. Recently, a soft magnetic film of 2.2 T or more has been energetically studied. Fe _x Co _1-x (0.6 ≦ x ≦ 0.8) is promising as a material exhibiting such a high saturation magnetic flux density. It is known that the FeCo alloy having this composition has a high saturation magnetic flux density of 2.4 T or more. However, when a FeCo alloy having this composition is formed into a thin film by a normal sputtering method, the coercive force becomes as high as 50 to 100 Oe and cannot be used as a magnetic head core material.

  Therefore, it is an important issue to reduce the coercivity in the hard axis direction without greatly reducing the saturation magnetic flux density of the FeCo alloy.

  Conventionally, in order to reduce the coercivity of an FeCo alloy, an alloy target in which a third component is added to FeCo or a composite target in which a third component chip is mounted on an FeCo alloy target is used. A method of performing reactive sputtering by introducing an additive gas such as gas or oxygen gas is known. The third component is a material that easily binds selectively to the additive gas, and has a function of preventing the additive gas from affecting the Fe and Co. However, in this method, unless a third component other than FeCo is introduced in an amount of 5% or more, good soft magnetic characteristics cannot be obtained, so that the saturation magnetic flux density of the produced film is inevitably greatly reduced.

  As another method, it has also been reported that soft magnetic properties are improved by using a soft magnetic film as a base film and a FeCo-based alloy film laminated thereon (see Non-Patent Document 1). There were restrictions. For this reason, there is a need for a base film that can exhibit good soft magnetic properties in an FeCo-based alloy film without any restrictions on the manufacturing process.

  As the recording density is improved, the magnetic domain control of the recording head has become important, and a large anisotropic magnetic field has been demanded.

In addition to the improvement of the magnetic characteristics as described above, in order to facilitate the design of the magnetic head, it is desirable to obtain stable magnetic characteristics with a wide range of film thickness.
K. Shintaku, K. Yamakawa, and K. Ouchi, "High-Bs Fe-Co-Al-O soft magnetic films," J. Appl. Phys., Vol. 93, no. 10, pp. 6474-6476, 2003.

  An object of the present invention is to provide a high saturation magnetic flux density soft magnetic material having a high saturation magnetic flux density, a low coercive force, and a large anisotropic magnetic field.

The high saturation magnetic flux density soft magnetic material according to the present invention has the following general formula _: M _{a a} M _1-a
(Where 0.4 ≦ a ≦ 0.95, and M is at least one selected from the group consisting of Fe, Ir, Pt, Cr, Rh, Ru, Pd, Ni, Co, Au, Cu, and Ag. Seeds)
In represented by a Mn-based alloy underlayer having a thickness of 0.2～20Nm, the following general formula _{(Fe x Co 1-x)} y (Al 2 O z) 1-y
(Where 0.6 ≦ x ≦ 0.8, 0 <(1-y) ≦ 0.05, 2 ≦ z ≦ 5)
And a film having a film thickness of 50 to 1000 nm.

  Since the soft magnetic material according to the present invention has a high saturation magnetic flux density, a low coercive force, and a large anisotropic magnetic field, when this is used as a magnetic head core material, information to a recording medium having a high coercive force is obtained. Can be easily written and a stable magnetic domain can be formed on the recording medium, so that the reproduction signal quality is improved. In addition, since desired magnetic characteristics can be obtained with a wide range of film thickness, the design margin and manufacturing margin of the magnetic head can be increased.

  Hereinafter, the high saturation magnetic flux density soft magnetic material according to the present invention will be described in detail.

In the high saturation magnetic flux density soft magnetic material according to the present invention, the base film is made of a Mn-based alloy. Specifically, MnFe alloy, MnIr alloy, MnPt alloy, MnCr alloy, MnRh alloy, MnRu alloy, MnPd alloy, MnNi alloy, MnCo alloy, MnAu alloy, MnCu alloy, MnAg alloy, MnRhRu alloy, MnFeRh alloy, MnPtPd alloy, Examples thereof include MnPtCr alloy and MnNiCr alloy. These Mn-based alloys need to reduce the coercivity of the high saturation magnetic flux density soft magnetic film when used as an underlayer for the following high saturation magnetic flux density soft magnetic film. Is represented by the general formula Mn _a M _1-a (M is at least one Fe, Ir, Pt, Cr, Rh, Ru, Pd, Ni, Co, Au, is selected from the group consisting of Cu and Ag) The Mn composition of the Mn-based alloy must be 0.4 ≦ a ≦ 0.95. Furthermore, it is preferable that 0.5 ≦ a ≦ 0.95 for an Mn-based alloy containing Ir, Rh and Ru, and 0.4 ≦ a ≦ 0.85 for an Mn-based alloy containing other elements.

The high saturation magnetic flux density soft magnetic film formed on the base film contains Fe _x Co _1-x (0.6 ≦ x ≦ 0.8) as a main component. It is known that FeCo having an appropriate composition reaches a maximum value of 2.45 T, which is the maximum value that can be obtained in an alloy system, by adjusting a sputtering target and film formation conditions. An FeCo alloy having a composition range represented by Fe _x Co _1-x (0.6 ≦ x ≦ 0.8) has a saturation magnetic flux density close to the above value. In the present invention, high saturation magnetic flux density having a composition containing 5% or less of Al ₂ O _z (2 ≦ z ≦ 5) with respect to Fe _x Co _1-x (0.6 ≦ x ≦ 0.8). A soft magnetic film is used. The Al ₂ O _z (2 ≦ z ≦ 5) content is preferably 0.5 to 5%. When the Al ₂ O _z (2 ≦ z ≦ 5) content is less than 0.5%, the coercive force in the hard axis direction tends to increase. When the Al ₂ O _z (2 ≦ z ≦ 5) content exceeds 5%, the saturation magnetic flux density tends to decrease.

High saturation flux density soft magnetic material according to the present invention, by forming on a Mn-based alloy underlayer of _{(Fe x Co 1-x)} y (Al 2 O z) 1-y film, the saturation magnetic flux density is 2 High saturation magnetic flux density and good soft magnetic properties of 3T or more, coercive force in the hard axis direction of 2 Oe or less, and anisotropic magnetic field of 20 Oe or more are exhibited.

  Since the high saturation magnetic flux density soft magnetic material of the present invention has a high saturation magnetic flux density, when it is used as a magnetic head core material, it becomes easy to write information on a recording medium having a high coercive force, Since stable magnetic domains can be formed on the recording medium, the reproduction signal quality is also improved.

In the high saturation flux density soft magnetic material according to the present invention, Mn-based alloy underlayer film thickness is _{0.2~20nm, (Fe x Co 1-} x) y (Al 2 O z) 1-y film with The thickness is preferably 50 to 1000 nm. When the film thickness is in the above range, the coercive force in the hard axis direction is 2 Oe or less. As described above, desired magnetic characteristics can be obtained in a wide range of film thicknesses, so that the design margin and manufacturing margin of the magnetic head can be increased. Note that the ratio of the film thickness of the base film to the total film thickness is preferably small, and the film thickness of the base film is preferably 5% or less, more preferably 1% or less.

In the present _{invention, (Fe x Co 1-x} ) y (Al 2 O z) 1-y film can be deposited by a sputtering method. Specifically, the following method can be used.

1) Sputtering is performed using a sintered target containing 5% or less of Al ₂ O _{3 in} FeCo.

2) Co-sputtering is performed using an FeCo alloy target and an Al ₂ O ₃ target.

3) Sputtering is performed using a composite target in which an Al ₂ O ₃ chip is attached on an FeCo alloy target.

In the high saturation magnetic flux density soft magnetic material according to the invention, the Al—O component may deviate from the stoichiometric composition depending on the manufacturing conditions. That is, the high saturation flux density soft magnetic material according to the present invention, if the prediction from the target composition, but it should be represented by the expression _{(Fe x Co 1-x)} y (Al 2 O 3) 1-y The film actually formed is
_{(Fe x Co 1-x)} y (Al 2 O z) 1-y
(Where 0.6 ≦ x ≦ 0.8, 0 <(1-y) ≦ 0.05, 2 ≦ z ≦ 5)
The composition range represented by the formula can be taken.

  Once the sputtering conditions are determined, a high saturation magnetic flux density soft magnetic material having desired magnetic characteristics can be manufactured stably thereafter.

(Example)
In the following examples, a high saturation magnetic flux density soft magnetic material having the configuration shown in FIG. 1 was produced. As shown in FIG. 1, a Mn alloy base film 2 and an FeCo film 3 are formed on a substrate 1.

Example 1
As targets, disc-shaped Mn _0.5 Pt _0.5 and (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 sintered bodies having a diameter of 100 mm and a thickness of 3 mm were used. A substrate in which silicon oxide was formed on the surface of a 10 mm square and 1 mm thick silicon was used.

  The above two targets and the substrate were fixed in a vacuum chamber of a six-target high-frequency magnetron sputtering apparatus (SPM-506 manufactured by Tokki), and the distance between the substrate and the target was adjusted to about 75 mm. In order to impart magnetic anisotropy to the soft magnetic film, a permanent magnet is disposed outside the substrate so that a magnetic field of 100 Oe or more is applied at the center of the substrate.

The inside of the vacuum chamber was evacuated to 2 × 10 ⁻⁵ Pa. Thereafter, Ar gas was introduced into the vacuum chamber, and the gas flow rate was adjusted so that the pressure was 1 Pa. High frequency sputtering was performed at a discharge power of 400 W and a discharge frequency of 13.56 MHz. On the substrate, an Mn _0.5 Pt _0.5 alloy target was used to deposit a base film of 1 nm, and a (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 alloy target was used to deposit an FeCo-based film of 400 nm.

As a comparative example, only an Fe ₇₀ Co ₃₀ film having a thickness of about 400 nm is formed on the substrate in the same procedure as described above, using only an Fe ₇₀ Co ₃₀ alloy target not containing Al ₂ O ₃ and without forming an MnPt underlayer. Deposited.

For reference, a (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 film having a thickness of about 400 nm was deposited on the substrate in the same procedure as above without forming the MnPt underlayer.

  The characteristics of the FeCo film prepared as described above were evaluated. VSM was used for the measurement.

FIG. 2 shows the magnetization curve of the soft magnetic material of this example having an MnPt underlayer and a (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 layer. The saturation magnetic flux density was 2.42 T, the coercivity in the hard axis direction was 0.3 Oe, and the anisotropic magnetic field was 25 Oe, indicating a high saturation magnetic flux density and good soft magnetic properties.

FIG. 3 shows the magnetization curve of only the Fe ₇₀ Co ₃₀ film. The saturation magnetic flux density was 2.45 T, and the coercive force in the hard axis direction was 50 Oe.

FIG. 4 shows the magnetization curve of only the (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 film. The saturation magnetic flux density was 2.42 T, and the coercive force in the hard axis direction was 3 Oe.

  2 to 4, it can be seen that the soft magnetic material of this example can significantly improve the soft magnetic properties of the FeCo-based film by providing a very thin MnPt underlayer.

Example 2
In the same procedure as in Example 1, the thickness of the MnPt base film formed on the substrate is fixed to 1 nm, and (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 film is formed thereon with various thicknesses. Deposited at.

FIG. 5 shows the relationship between the coercive force Hch in the hard axis direction and the film thickness of the (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 film for the obtained soft magnetic material. FIG. 5 shows that the coercive force Hch in the hard axis direction is 1 Oe or less when the thickness of the (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 film is 50 to 1000 nm.

Further, in all soft magnetic materials having a film thickness of (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _{0.01 in the} range shown in FIG. 5, the saturation magnetic flux density is substantially constant at 2.42 T, which is anisotropic. The magnetic field was 20 Oe or more.

Example 3
In the same procedure as in Example 1, MnPt underlayers were deposited on the substrate with various thicknesses, and (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 layer was fixed on the thickness of about 400 nm on the substrate. And deposited.

  FIG. 6 shows the relationship between the coercive force Hch in the hard axis direction and the film thickness of the MnPt underlayer for the obtained soft magnetic material. 6 that the coercive force Hch in the hard axis direction is 1 Oe or less when the thickness of the MnPt underlayer is 0.2 to 20 nm.

  Further, in all soft magnetic materials in which the film thickness of the MnPt underlayer was in the range shown in FIG. 6, the saturation magnetic flux density was almost constant at 2.42 T, and the anisotropic magnetic field was 20 Oe or more.

Example 4
Other than using (Fe _0.70 Co _0.30 ) _y (Al ₂ O ₃ ) _1-y (0.005 ≦ (1-y) ≦ 0.06) sintered bodies having different Al ₂ O ₃ contents as targets, A (Fe _0.70 Co _0.30 ) _y (Al ₂ O ₃ ) _1-y film was deposited on the substrate via the MnPt underlayer in the same procedure as in Example 1.

FIG. 7 shows the relationship between the saturation magnetic flux density and the coercive force Hch in the hard axis direction and the Al ₂ O ₃ content in the FeCo-based film for the obtained soft magnetic material. FIG. 7 shows that when the Al ₂ O ₃ content is 0.5 to 3%, the saturation magnetic flux density is 2.3 T or more and the coercive force Hch in the hard axis direction is 1 Oe or less.

Further, in all soft magnetic materials in which the composition of the (Fe _0.70 Co _0.30 ) _y (Al ₂ O ₃ ) _{1 -y} film is in the range shown in FIG. 7, the anisotropic magnetic field was 20 Oe or more.

Example 5
Mn _a M _1-a (0.4 ≦ a ≦ 0.95) in which the alloy component M is Fe, Ir, Pt, Cr, Rh, Ru, Pd, Ni, Co, Au, Cu, or Ag is used as a target. In the same procedure as in Example 1, a Mn-based alloy base film was deposited on the substrate, and a (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 film was deposited thereon.

  Table 1 shows the values of saturation magnetic flux density (Bs), hard axis coercivity (Hch), and anisotropic magnetic field (Hk) for the obtained soft magnetic material.

Table 1 shows that in all soft magnetic materials, the saturation magnetic flux density is 2.3 T or more, the coercive force in the hard axis direction is 2 Oe or less, and the anisotropic magnetic field is 20 Oe or more.

Sectional drawing of the high saturation magnetic flux density soft magnetic material which concerns on this invention. The figure which shows the magnetization curve of the soft magnetic material containing the MnPt base film and the (Fe _0.70 Co _0.30 ) _0.99 (Al ₂ O ₃ ) _0.01 film in Example 1. Shows the magnetization curves of Fe ₇₀ Co ₃₀ film only. _{(Fe 0.70 Co 0.30) 0.99 (} Al 2 O 3) shows the magnetization curve of only _0.01 membrane. Diagram showing the relationship between the thickness of the example for the soft magnetic material in the 2, the direction of hard axis coercivity _{(Fe 0.70 Co 0.30) 0.99 (} Al 2 O 3) 0.01 film. The figure which shows the relationship between the coercive force of a hard-axis direction, and the film thickness of a MnPt base film about the soft magnetic material in Example 3. FIG. The soft magnetic material according to Example 4, shows the relationship between the Al ₂ O ₃ content in the saturated magnetic flux density and the coercivity in the hard axis direction and FeCo-based film.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Mn system alloy base film, 3 ... FeCo system film.

Claims (1)

The following general formula Mn _a M _1-a
(Where 0.4 ≦ a ≦ 0.95, and M is at least one selected from the group consisting of Fe, Ir, Pt, Cr, Rh, Ru, Pd, Ni, Co, Au, Cu, and Ag. Seeds)
In represented by a Mn-based alloy underlayer having a thickness of 0.2～20Nm, the following general formula _{(Fe x Co 1-x)} y (Al 2 O z) 1-y
(Where 0.6 ≦ x ≦ 0.8, 0 <(1-y) ≦ 0.05, 2 ≦ z ≦ 5)
And a high saturation magnetic flux density soft magnetic material characterized by including a film having a film thickness of 50 to 1000 nm.

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