JP2008172067A - Manufacturing method of soft magnetic thin film, same soft magnetic thin film, magnetic head, and vertical magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a soft magnetic thin film, the soft magnetic thin film itself, a magnetic head, and a vertical magnetic recording medium wherein its characteristics of a saturated magnetic flux density B<SB>s</SB>not smaller than 24.5 kG and an anisotropic magnetic field H<SB>k</SB>not smaller than 15.50e can be realized even when adding no third element to it. <P>SOLUTION: The manufacturing method of the soft magnetic thin film includes a backing film manufacturing step for film-manufacturing a non-magnetic backing film 12 on a non-magnetic substrate 11 and a magnetic film manufacturing step for film-manufacturing an Fe-Co magnetic film 13 on the non-magnetic backing film 12. Hereupon, the magnetic film manufacturing step includes an ion-irradiation-based film manufacturing step for film-manufacturing the Fe-Co magnetic film 13 while irradiating an assist-ion beam IBa on the non-magnetic backing film 12 and a heat treating step for heat-treating the Fe-Co magnetic film 13 after ion-irradiation-based film manufacturing while applying a magnetic field to it. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a soft magnetic thin film manufacturing method, a soft magnetic thin film, a magnetic head, and a perpendicular magnetic recording medium.

  In recent years, in order to reduce the size and capacity of a recording apparatus, and to increase the transfer rate associated therewith, the coercive force and density of a recording medium have been increased and the operating frequency of a magnetic head has been increased.

In order to perform saturation recording on a high coercive force medium, it is necessary to apply a soft magnetic thin film having a high saturation magnetic flux density B _s to the recording magnetic pole of the magnetic head. Further, by adopting a two-layer perpendicular magnetic recording medium as a recording medium and applying a soft magnetic thin film having a high saturation magnetic flux density B _s to the soft magnetic layer, it is possible to increase the magnetic recording density.

For the bandwidth of the operating frequency of the magnetic head, it is necessary to increase the ferromagnetic resonance frequency f _r of the soft magnetic layer of the recording magnetic pole. Ferromagnetic resonance frequency f _r of the soft magnetic thin film having in-plane uniaxial anisotropy is represented as the Equation 1 using the saturation flux density B _s and anisotropy field H _k. Therefore, by increasing the saturation magnetic flux density B _s and the anisotropic magnetic field H _k , the ferromagnetic resonance frequency _fr of the magnetic head can be increased and the operating frequency of the magnetic head can be broadened.

A general Fe—Co magnetic film as a soft magnetic thin film has a high saturation magnetic flux density B _s of 24.5 kG when the Co composition ratio is 25 to 35%, but the magnetostriction is 3 to 8 × 10 ⁻⁵ . Since it is large, it is not easy to realize the characteristic that the coercive force H _c required for the soft magnetic thin film is small and the anisotropic magnetic field H _k is large.

Stanford University X. Wang et al. Realized a saturation magnetic flux density B _s = 24.5 kG and a ferromagnetic resonance frequency f _r = 1.5 GHz by using a Ni—Fe thin film as a base film and adding nitrogen to the Fe—Co film. It is reported that it can be done (for example, see Non-Patent Document 1).

With this report as an opportunity, research on Fe—Co soft magnetic thin film materials having a high saturation magnetic flux density B _s using a Ni—Fe thin film as an underlayer has been vigorously conducted.

Shinya et al. Of Akita Advanced Technology Research Institute added a small amount of Al ₂ O ₃ to Fe-Co and used a soft magnetic underlayer consisting of a Ni-Fe thin film or a Co-Zr-Nb thin film. A soft magnetic thin film having a large B _s of 24 kG and a coercive force H _c of 1 Oe or less has been successfully developed (for example, see Non-Patent Document 2).

Further, in an Fe—Co—Al—O film deposited by ion beam sputtering using a base material obtained by adding 1% Al ₂ O ₃ to an Fe ₇₀ Co ₃₀ (at%) alloy, Cu, Au, Ag, even using a non-magnetic base film such as Al or Ru, saturation magnetic flux density B _s is more than 23 kg, also soft magnetic film capable of ferromagnetic resonance frequency f _r is realize the above characteristics 1GHz is obtained reported (For example, see Non-Patent Document 3).
SX Wang, NX Sun, M. Yamaguchi and S. Yabukami, Nature, Vol.407, p.150-151, 2000 Shintaku, Yamakawa, Ouchi, IEICE technical report, 2002, MR2002-20 N. Hayashi, Y. Miyamoto, K. Machida, and T. Tamaki, Journal of Magnetism and Magnetic Materials, 287, pp.387-391, 2005

However, such a manufacturing technique of a conventional soft magnetic thin film, can be realized Fe-Co magnetic film having a high saturation magnetic flux density B _s and a high ferromagnetic resonance frequency f _r without adding a third element There wasn't.

The present invention has been made to solve the above-described conventional problems. Even when no third element is added, the saturation magnetic flux density B _s is 24.5 kG or more, and the anisotropy magnetic field H _k is 15.5 Oe or more. An object of the present invention is to provide a method for producing a soft magnetic thin film capable of realizing the above characteristics.

[First invention]
The method for producing a soft magnetic thin film of the present invention comprises a base film forming step of forming a nonmagnetic base film on a nonmagnetic substrate, and an iron cobalt (Fe—Co) magnetic film is formed on the nonmagnetic base film. A method for producing a soft magnetic thin film including a magnetic film forming step, wherein the magnetic film forming step forms the Fe—Co magnetic film while irradiating an assist ion beam on the nonmagnetic underlayer. An ion irradiation film forming step, and a heat treatment step in which heat treatment is performed while applying a magnetic field to the Fe-Co magnetic film after ion irradiation film formation.

This manufacturing method makes it possible to manufacture a soft magnetic thin film having a high saturation magnetic flux density B _s and a high anisotropic magnetic field H _k even when no third element is added.

[Second invention]
In the method for producing a soft magnetic thin film according to the present invention, the assist ion beam has a beam voltage of 50 to 250 volts.

  With this manufacturing method, an Fe—Co magnetic film having a body-centered cubic structure and having a (110) plane spacing of 2.028 to 2.031 angstroms can be manufactured.

[Third invention]
In the soft magnetic thin film manufacturing method of the present invention, the base film forming step forms a copper (Cu) film as the nonmagnetic base film.

  With this manufacturing method, an Fe—Co magnetic film having a body-centered cubic structure and having a (110) plane spacing of 2.028 to 2.031 angstroms can be manufactured.

[Fourth Invention]
The soft magnetic thin film of the present invention has a nonmagnetic underlayer formed on a nonmagnetic substrate, a nonmagnetic underlayer formed on the nonmagnetic underlayer, has a body-centered cubic structure, and has a (110) spacing of 2 And a Fe—Co magnetic film in the range of 0.028 to 2.031 angstroms.

With this configuration, even when the third element is not added, it is possible to realize the characteristics that the saturation magnetic flux density B _s is 24.5 kG or more and the anisotropic magnetic field H _k is 15.5 Oe or more.

[Fifth Invention]
The magnetic head of the present invention has a configuration including the soft magnetic thin film described in the fourth invention.

With this configuration, even when the third element is not added, it is possible to realize the characteristics that the saturation magnetic flux density B _s is 24.5 kG or more and the anisotropic magnetic field H _k is 15.5 Oe or more.

[Sixth Invention]
The perpendicular magnetic recording medium of the present invention has a configuration including the soft magnetic thin film described in the fourth invention.

With this configuration, even when the third element is not added, it is possible to realize the characteristics that the saturation magnetic flux density B _s is 24.5 kG or more and the anisotropic magnetic field H _k is 15.5 Oe or more.

In the present invention, by forming an Fe—Co magnetic film while irradiating an assist ion beam with a beam voltage of 50 to 250 volts on a nonmagnetic undercoat film, the saturation magnetic flux density B _s can be obtained even when no third element is added. It is possible to provide a method for producing a soft magnetic thin film capable of realizing characteristics of 24.5 kG or more and an anisotropic magnetic field H _k of 15.5 Oe or more.

  Below, the soft-magnetic thin film 1 manufactured by the manufacturing method of the soft-magnetic thin film which concerns on this invention is demonstrated using drawing. FIG. 1 is a block diagram showing the structure of the soft magnetic thin film 1.

  The method for producing a soft magnetic thin film according to the present invention includes a base film forming step of forming a nonmagnetic base film 12 on a nonmagnetic substrate 11, and a Fe—Co magnetic film 13 formed on the nonmagnetic base film 12. A method for producing a soft magnetic thin film, comprising: forming a Fe—Co magnetic film 13 while irradiating an assist ion beam IBa on a nonmagnetic underlayer 12. An ion irradiation film forming step, and a heat treatment step in which a heat treatment is performed while applying a magnetic field to the Fe—Co magnetic film 13 after the ion irradiation film formation.

  The beam voltage of the assist ion beam IBa is 50 to 250 volts. The base film forming step is a step of forming a Cu film as the nonmagnetic base film 12.

  That is, the soft magnetic thin film 1 manufactured by the manufacturing method according to the present invention is formed on the nonmagnetic base film 12 and the nonmagnetic base film 12, and has a body-centered cubic structure. And an Fe—Co magnetic film 13 having a (110) spacing of 2.028 to 2.031 angstroms (Å).

  FIG. 2 is a schematic diagram showing the configuration of the film forming apparatus 2 for the soft magnetic thin film 1 according to the present invention.

  That is, the film forming apparatus 2 includes a film forming ion source 21 that emits a film forming ion beam IB, a rotatable target rotating mechanism 22 that holds a target from which the sputtered particles S are knocked out by the film forming ion beam IB, A rotatable substrate rotation mechanism 23 having a magnet 231 and holding the non-magnetic substrate 11, an assist ion source 24 that emits an assist ion beam IBa, a roughing rotary pump (not shown), And a cryopump for vacuum (not shown).

  A hollow cathode type ion source was used as the ion source 21 for film formation and the ion source 24 for assist. Note that krypton gas was used as an ion gas for the film forming ion beam IB and the assist ion beam IBa.

The target rotating mechanism 22 can hold four different materials on four surfaces, and Cu, Au, Al, Ag, Ti or Ta, Fe—Co magnetic film as a material for the nonmagnetic underlayer film 12. As a material for No. 13, Fe ₇₀ Co ₃₀ having a purity of 99.99% is provided. By rotating the target rotation mechanism 22, a material used for film formation can be selected as appropriate.

  The nonmagnetic substrate 11 used for film formation was placed in parallel with the target, and rotated at 5 rotations per minute by the substrate rotation mechanism 23. As the nonmagnetic substrate 11, a silicon wafer with a surface oxide film and barium borosilicate glass (Corning 7059 (trademark)), alumina titanium carbide, or the like was used.

For the non-magnetic underlayer 12, the inside of the film forming apparatus is evacuated to 2 × 10 ⁻⁸ Torr or less using a rotary pump and a cryopump, and then the beam voltage of the ion source 21 for film forming is set to 850 V, and the beam current is set to 100 mA (current density 50 A / m ² , where the current density is the beam current flowing between the anode and ground divided by the area emitted from the ion source), and the krypton gas pressure 2 × 10 ^{− The} film was formed at ⁴ Torr, and the film thickness was 5 nm.

For the Fe—Co magnetic film 13, the inside of the film forming apparatus is evacuated to 2 × 10 ⁻⁸ Torr or less using a rotary pump and a cryopump, and then the beam voltage of the film forming ion source 21 is 1200 V, the beam current. Was set to 100 mA (current density 50 A / m ² ). While applying a magnetic field of 150 Oe to the nonmagnetic substrate 11 by the magnet 231, the film was formed at a krypton gas pressure of 2 × 10 ⁻⁴ Torr, and the film thickness was set to 100 nm.

When the Fe—Co magnetic film 13 is formed, an assist ion beam IBa is generated from the assist ion source 24 with krypton gas at a beam voltage of 50 to 300 V and a beam current of 10 to 40 mA (current density of 5 to 20 A / m ² ). The assist ion beam IBa was applied to the nonmagnetic underlayer film 12 formed on the nonmagnetic substrate 11 at an incident angle of 45 degrees.

After film formation, the Fe—Co magnetic film 13 was heat-treated at 325 ° C. for 1 hour while applying a magnetic field of 1 kOe in a vacuum of 5 × 10 ⁻⁷ Torr or less. By performing the above heat treatment, the soft magnetic properties are improved. In addition, when the soft magnetic thin film 1 is applied to a magnetic head, it has heat resistance against a processing temperature (for example, 280 ° C.) during the magnetic head manufacturing process.

The saturation magnetic flux density B _s , coercive force H _c , and anisotropic magnetic field H _{k of the} produced soft magnetic thin film 1 were determined from the magnetization characteristics measured using a vibrating sample magnetometer. In this embodiment, the saturation magnetic flux density B _s is evaluated by the magnetic flux density B ₁₀₀ in a magnetic field of ₁₀₀ Oe.

FIG. 3 is a graph showing an example of the magnetization characteristics of the soft magnetic thin film 1 according to the present invention. The sample is used in Example 3 described later. In FIG. 3, HA (solid line) and EA (dotted line) indicate magnetization characteristics in the hard axis direction and the easy axis direction, respectively. From FIG. 3, H _c = 2.5 Oe, H _k = 18.3 Oe, B ₁₀₀ = 24.5 kG in the hard axis direction, and H _c = 9.5 Oe, B ₁₀₀ = 24. It turns out that it is 5kG.

4 and 5 are tables showing the manufacturing conditions and various characteristics of Examples 1 to 10 and Comparative Examples 11 to 28 of the soft magnetic thin film 1 according to the present invention. Note that the symbol “-” in the “heat treatment temperature” column in FIG. 5 indicates that heat treatment is not performed. The values of H _c , H _k , and B _s shown in FIGS. 4 to 9 are all determined from the magnetization characteristics in the hard axis direction.

Comparative Example 13 to 16 in FIG. 5, the assist ion beam IBa the beam voltage (hereinafter, referred to as an assist voltage) in V _a is 0, Cu, Ag, Au, Al is used non-magnetic undercoat layer 12, the 325 ° C. When heat treatment is performed, the characteristics of H _c ≦ 4.4 Oe are obtained, but it can be seen that H _k ≦ 8.2 Oe. 4 and 5 that B ₁₀₀ = 24.5 kG can be achieved without adding the third element.

FIG. 6 is a graph showing the relationship between the coercive force H _c of the soft magnetic thin film 1 according to the present invention and the (110) plane distance d ₍₁₁₀₎ , and all the samples of Examples 1 to 10 and Comparative Examples 11 to 28 are shown. Is plotted for. From this graph, the samples of Examples 1 to 10 and Comparative Examples 13 to 16 and 18 in which the (110) plane distance d ₍₁₁₀₎ is in the range of 2.028 to 2.031 mm are characteristics of H _c ≦ 5.2 Oe. It can be seen that

FIG. 7 is a graph showing the relationship between the anisotropic magnetic field H _k and the (110) spacing d ₍₁₁₀₎ of the soft magnetic thin film 1 according to the present invention, and all of Examples 1 to 10 and Comparative Examples 11 to 28. It is what plotted about the sample of this. From this graph, it can be seen that the samples of Examples 1 to 10 in which the (110) plane distance d ₍₁₁₀₎ is in the range of 2.028 to 2.031 mm exhibit characteristics of H _k ≧ 15.5 Oe.

FIG. 8 is a graph showing the relationship between the coercive force H _c and the assist voltage V _a of the soft magnetic thin film 1 according to the present invention. In FIGS. 6 and 7, H _c ≦ 5.2 Oe and H _k ≧ 15.5 Oe. In addition to the samples of Examples 1 to 10 (the heat treatment temperature is 325 ° C. and the nonmagnetic underlayer film 12 is a Cu film), the heat treatment temperature is 325 ° C. and the nonmagnetic underlayer film 12 is a Cu film. It is a plot of sample data. From this graph, the heat treatment temperature is 325 ° C., the non-magnetic undercoat layer 12 is a Cu film, when the assist voltage V _a is in the range of 50～250V (Examples 1 to 10), the characteristics of H _c ≦ 2.5Oe It turns out that it is obtained.

FIG. 9 is a graph showing the relationship between the anisotropic magnetic field H _k and the assist voltage V _a of the soft magnetic thin film 1 according to the present invention. As in FIG. 8, the heat treatment temperature is 325 ° C. in FIGS. It plots about the sample (Examples 1-10, Comparative Examples 13 and 18) whose nonmagnetic base film 12 is Cu film | membrane. From this graph, the heat treatment temperature is 325 ° C., the non-magnetic undercoat layer 12 is a Cu film, when the assist voltage V _a is in the range of 50～250V (Examples 1 to 10), the characteristics of H _k ≧ 15.5Oe It turns out that it is obtained.

Therefore, by assisting voltage V _a during film formation to irradiation an assist ion beam IBa ranges 50～250V, soft magnetic thin film 1 non-magnetic undercoat film 12 is a Cu film (110) face spacing d _It can be seen that ₍₁₁₀₎ has characteristics of about 2.030 mm, B ₁₀₀ = 24.5 kG, H _c ≦ 2.5 Oe, and H _k ≧ 15.5 Oe. The value of the ferromagnetic resonance frequency f _r at this time is approximately 1.8GHz.

  Since the easy magnetization axis direction of the soft magnetic thin film 1 is the magnetic field application direction during film formation or the magnetic field application direction during heat treatment, the easy magnetization axis direction can be set in a desired direction. This feature is useful when applied to a magnetic head or a perpendicular magnetic recording medium.

  The magnetic head 3 shown in FIG. 10 includes a return yoke 31 and a recording magnetic pole 32 made of the soft magnetic thin film 1 according to the present invention. A magnetic circuit is constituted by the return yoke 31, the recording magnetic pole 32, and the perpendicular magnetic recording medium D, and data is recorded by magnetizing the perpendicular magnetic recording medium D. In FIG. 10 and FIG. 11 shown later, the description of the reproducing head is omitted.

  Here, by making the track width direction indicated by W in FIG. 10 parallel to the easy magnetization axis of the soft magnetic thin film, the magnetic field intensity from the recording magnetic pole 32 can be increased, and the recording sensitivity to the perpendicular magnetic recording medium D can be increased. It becomes possible to improve.

  FIG. 11 is a cross-sectional view showing an example in which the soft magnetic thin film 1 according to the present invention is applied to the magnetic head 3. As shown in FIGS. 11A, 11B, and 11C, the soft magnetic thin film 1 of the present invention can be applied to part or all of the return yoke 31 and the recording magnetic pole 32. FIG.

12 includes a nonmagnetic substrate 41, the soft magnetic thin film 1 according to the present invention, an intermediate layer 42, a perpendicular magnetic recording layer 43, and a protective film. The layer 44 is included, and by setting the direction of the easy axis 45 of the Fe—Co magnetic film 13 of the soft magnetic thin film 1 to the radial direction, it is possible to suppress noise accompanying the domain wall movement of the Fe—Co magnetic film. it can. Furthermore, since the soft magnetic thin film 1 has a high saturation magnetic flux density B _s , the double-layer perpendicular magnetic disk 4 can perform high-density magnetic recording.

As described above, according to the method for manufacturing a soft magnetic thin film of the embodiment of the present invention, the saturation magnetic flux density B _s is 24.5 kG or more and the anisotropic magnetic field H _k is 15.4 even when no third element is added. A soft magnetic thin film having a characteristic of 5 Oe or more can be realized, and can be applied to a magnetic head and a perpendicular magnetic recording medium.

As described above, the method for producing a soft magnetic thin film according to the present invention includes forming a Fe—Co magnetic film on a nonmagnetic underlayer while irradiating an assist ion beam with a beam voltage of 50 to 250 volts. Even when three elements are not added, the magnetic head has the effect that the saturation magnetic flux density B _s is 24.5 kG or more and the anisotropic magnetic field H _k is 15.5 Oe or more, and has a soft magnetic thin film. It is effective for a perpendicular magnetic recording medium.

The block diagram which shows the structure of the soft-magnetic thin film based on this invention The schematic diagram which shows the structure of the film-forming apparatus of the soft-magnetic thin film based on this invention The graph which shows an example of the magnetization characteristic of the soft-magnetic thin film based on this invention Table showing manufacturing information and various characteristics of Examples 1 to 10 of the soft magnetic thin film according to the present invention. Table showing manufacturing information and various characteristics of Comparative Examples 11 to 28 of the soft magnetic thin film according to the present invention. The graph which shows the relationship between the coercive force of the soft-magnetic thin film based on this invention, and a (110) plane space | interval. The graph which shows the relationship between the anisotropic magnetic field of the soft-magnetic thin film which concerns on this invention, and a (110) plane space | interval The graph which shows the relationship between the coercive force and assist voltage of the soft-magnetic thin film which concerns on this invention The graph which shows the relationship between the anisotropic magnetic field and assist voltage of the soft-magnetic thin film which concerns on this invention Schematic diagram showing the configuration of a magnetic head to which a soft magnetic thin film according to the present invention is applied. Sectional drawing which shows the example by which the soft-magnetic thin film based on this invention is applied to a magnetic head Schematic diagram showing the configuration of a double-layered perpendicular magnetic disk to which a soft magnetic thin film according to the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Soft magnetic thin film 3 Magnetic head 4 Double layer perpendicular magnetic disk 11 Nonmagnetic board | substrate 12 Nonmagnetic base film 13 Fe-Co magnetic film

Claims (6)

A base film forming step of forming a nonmagnetic base film on a nonmagnetic substrate;
A method for producing a soft magnetic thin film, comprising: a magnetic film forming step of forming an iron cobalt (Fe—Co) magnetic film on the nonmagnetic underlayer,
The magnetic film forming step includes ion irradiation film forming step of forming the Fe-Co magnetic film while irradiating an assist ion beam on the nonmagnetic underlayer.
A method for producing a soft magnetic thin film, comprising: a heat treatment step of performing heat treatment while applying a magnetic field to the Fe—Co magnetic film after ion irradiation film formation. The method of manufacturing a soft magnetic thin film according to claim 1, wherein a beam voltage of the assist ion beam is 50 to 250 volts. 3. The method of manufacturing a soft magnetic thin film according to claim 1, wherein the base film forming step is a step of forming a copper (Cu) film as the nonmagnetic base film. A nonmagnetic underlayer film formed on a nonmagnetic substrate;
A soft magnetic thin film comprising an Fe—Co magnetic film formed on the nonmagnetic underlayer, having a body-centered cubic structure and having a (110) plane spacing in the range of 2.028 to 2.031 angstroms. A magnetic head comprising the soft magnetic thin film according to claim 4. A perpendicular magnetic recording medium comprising the soft magnetic thin film according to claim 4.

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