JP2005294756A - Soft magnetic thin film, method of manufacturing the same, and magnetic head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft magnetic thin film capable of implementing a property in which resonant frequency fr is 1GHz or more and saturation magnetic flux density Bs is 23kG or more even in the case where a non-magnetic base film is used, the method of manufacturing the same, and a magnetic head. <P>SOLUTION: A structure in which a base film 120 and a magnetic film 130 are formed on a substrate 110 is used as a basic structure. One of an Au film, an Ag film, an Al film, and an Ru film is used as the base film 120. An Fe-Co-Al-O magnetic film is used as the magnetic film 130. This make it possible to implement even by a structure having a non-magnetic base layer a soft magnetic property comparable to one implemented by a structure having a magnetic base layer. A multilayer film structure, in which the Fe-Co-aluminum-O magnetic film is stacked such that one of the Au film, the Ag film, the Al film, and the Ru film is sandwiched as an interlayer between layers, is made. This allows the invention to have a structure capable of alleviating the influence of a demagnetizing field. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a soft magnetic thin film for a magnetic head used in a VCR (Video Cassette Recorder), a magnetic disk recording apparatus, etc., a manufacturing method thereof, and a magnetic head.

In recent years, in order to increase the density of magnetic recording in response to the demand for smaller and larger capacity recording devices, higher coercivity of recording media and narrower tracks of magnetic heads have been promoted, resulting in higher transfer rates. For this reason, the operation frequency of the magnetic head is being widened. In order to perform saturation recording on a high coercive force medium, a soft magnetic thin film for a recording head magnetic pole having a high saturation magnetic flux density is required. Actually, in a fixed disk device such as an HDD (Hard Disk Drive), as the recording density is improved, the recording head magnetic pole material is changed from a ferrite having a saturation magnetic flux density Bs of 5 kG to 10 kG Ni ₈₁ Fe ₁₉ , 16 kG Ni ₅₀ Fe. It has changed to ₅₀ .

In the future, in order to improve the recording density, a soft magnetic thin film having a larger saturation magnetic flux density Bs is required. The Fe—Co thin film has a high saturation magnetic flux density Bs of 24.5 kG in a composition of 25 to 35 at% Co, but its magnetostriction is as large as 3 to 8 × 10 ⁻⁵ and it is not easy to derive soft magnetic properties. Stanford University X. Wang et al. Can realize a saturation magnetic flux density Bs = 24.5 kG and a ferromagnetic resonance frequency fr = 1.5 GHz by using a Ni—Fe thin film as a base film and adding nitrogen during the Fe—Co film formation. (For example, refer nonpatent literature 1.).

With this report as an opportunity, research on Fe—Co soft magnetic thin film materials having a high saturation magnetic flux density Bs by using a Ni—Fe thin film as an underlayer has been vigorously conducted. Fujitsu's Ikeda et al. Developed a soft magnetic thin film having a magnetic property of saturation magnetic flux density Bs = 22 kG and coercive force Hc = 1 Oe using a target composed of Fe ₈₀ Co ₂₀ and Al ₂ O ₃ (for example, (See Patent Document 2). Shinta et al., Akita Prefectural Advanced Technology Research Institute, add a small amount of Al ₂ O ₃ to the Fe—Co material, and use a soft magnetic underlayer made of Ni—Fe thin film or Co—Zr—Nb thin film as the underlayer. Has succeeded in developing a soft magnetic thin film having a saturation magnetic flux density Bs of 24 kG and a coercive force Hc of 1 Oe or less (see, for example, Non-Patent Document 3).

In order to broaden the operating frequency of the magnetic head, it is necessary to improve the frequency characteristics of the effective permeability μ ′ of the magnetic head material. Theoretically, by increasing the saturation magnetic flux density Bs and the anisotropic magnetic field Hk, the resonance frequency fr can be increased and the resonance loss can be decreased, and excellent frequency characteristics of μ ′ can be realized. Onuma et al. Of the Institute for Electromagnetic Materials have reported that the Co—Al—O granular structure film exhibits a resonance frequency fr of 1 GHz or higher and μ ′ at 500 MHz is 100. Bs is as small as about 10 kG (see Non-Patent Document 4, for example).
S. X. One, N. X. Sun, M. Yamaguchi, S. Yabukami: Nature, Vol. 407, pp. 150-151, 2000 (SX Wang, NX Sun, M. Yamaguchi and S. Yabukami: Nature, Vol. 407, pp. 150-151, 2000. ) S. Ikeda, Ai. Tagawa, Wai. Uehara, tea. Indentation, Jay. Kane, M. Kakei, A. Chikazawa: IEE, Transactions on Magnetics, Vol. 38, No. 5, pp. 2219-2221, 2002 (S. Ikeda, I. Tagawa, Y. Uehara, T. Kubomiya, J. Kane, M. et al. Kakei, A. Chikazawa: IEEE Tran Magn., Vol. 38, No. 5, pp. 2219-2221, 2002) Shintaku, Yamakawa, Ouchi: IEICE technical report, MR2002-20, 2002 Onuma, Mitani, Fujimori, Masumoto: Journal of Applied Magnetics Society of Japan, Vol. 20, No. 2, pp. 489-492, 1996

  However, such a conventional soft magnetic thin film manufacturing technique requires a soft magnetic thin film for a recording head having a high saturation magnetic flux density Bs and a high resonance frequency fr. Even when a Co—Al—O magnetic film is formed, it is difficult to produce a soft magnetic thin film having a high saturation magnetic flux density Bs and a high resonance frequency fr.

  The present invention has been made to solve such a problem. Even when a nonmagnetic underlayer is used, the present invention is a software that can realize the characteristics that the saturation magnetic flux density Bs is 23 kG or more and the resonance frequency fr is 1 GHz or more. A magnetic thin film, a manufacturing method thereof, and a magnetic head are provided.

  In view of the above points, the invention according to claim 1 has a configuration in which an Au film is formed as a base film on a substrate, and an Fe—Co—Al—O magnetic film is formed on the Au film. doing.

  With this configuration, it is possible to realize a soft magnetic thin film capable of having characteristics of a saturation magnetic flux density Bs of 23 kG or more and a resonance frequency fr of 1 GHz or more even when a nonmagnetic underlayer is used.

  According to a second aspect of the present invention, an Ag film is formed as a base film on a substrate, and an Fe—Co—Al—O magnetic film is formed on the Ag film.

  With this configuration, it is possible to realize a soft magnetic thin film capable of having characteristics of a saturation magnetic flux density Bs of 23 kG or more and a resonance frequency fr of 1 GHz or more even when a nonmagnetic underlayer is used.

  According to a third aspect of the present invention, an Al film is formed as a base film on a substrate, and a Fe—Co—Al—O magnetic film is formed on the Al film.

  With this configuration, it is possible to realize a soft magnetic thin film capable of having characteristics of a saturation magnetic flux density Bs of 23 kG or more and a resonance frequency fr of 1 GHz or more even when a nonmagnetic underlayer is used.

  According to a fourth aspect of the present invention, a Ru film is formed as a base film on a substrate, and an Fe—Co—Al—O magnetic film is formed on the Ru film.

  With this configuration, it is possible to realize a soft magnetic thin film capable of having characteristics of a saturation magnetic flux density Bs of 23 kG or more and a resonance frequency fr of 1 GHz or more even when a nonmagnetic underlayer is used.

The invention according to claim 5 is the structure according to any one of claims 1 to 4, wherein the undercoat film has a thickness in the range of not less than 0.5 nm and not more than 5 nm. Have.
With this configuration, in addition to the effect of any one of claims 1 to 4, it is possible to realize a soft magnetic thin film capable of making soft magnetic characteristics suitable.

The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the Fe—Co—Al—O magnetic film is an Au film, an Ag film, an Al film, or a Ru film. It has a configuration in which any one of the intermediate layers is separated and stacked.
With this configuration, in addition to the effect of any one of claims 1 to 5, any one of an Au film, an Ag film, an Al film, and a Ru film is used as an intermediate layer, so that the Ni-Fe film In addition to the impossible magnetic domain control, the element Au, Ag, Al or Ru constituting the intermediate layer is a non-magnetic material, so that the leakage magnetic flux at the end of the adjacent magnetic film can be reduced and the magnetic permeability is lowered. Thus, it is possible to realize a soft magnetic thin film capable of avoiding problems caused by the magnetic domain structure such as generation of noise.

  The invention according to claim 7 is the structure according to any one of claims 1 to 6, wherein the soft magnetic thin film is manufactured by heat treatment in a magnetic field within a temperature range of 250 ° C. to 420 ° C. have.

  With this configuration, in addition to the effect of any one of claims 1 to 6, the easy axis of magnetization can be set to a desired direction by the direction of the magnetic field applied during film formation or heat treatment. A magnetic thin film can be realized.

  The invention according to claim 8 has a configuration using the soft magnetic thin film according to any one of claims 1 to 7 as the soft magnetic thin film of the magnetic head.

  With this configuration, it is possible to realize a magnetic head having a high-performance soft magnetic material having a saturation magnetic flux density Bs of 23 kG or more and a resonance frequency fr of 1 GHz or more even when a nonmagnetic underlayer is used.

  The invention according to claim 9 is a method of heat-treating the soft magnetic film according to any one of claims 1 to 6 in a magnetic field within a temperature range of 250 ° C. to 420 ° C.

  By this method, even when a nonmagnetic underlayer film is used, a soft magnetic thin film having characteristics of a saturation magnetic flux density Bs of 23 kG or more and a resonance frequency fr of 1 GHz or more can be generated and applied during film formation or heat treatment. The easy axis direction of magnetization can be set to a desired direction depending on the magnetic field direction.

  The present invention provides a soft magnetic thin film having an effect that a saturation magnetic flux density of 23 kG or more and a resonance frequency of 1 GHz or more can be realized even when a nonmagnetic underlayer is used, a manufacturing method thereof, and a magnetic head. It is something that can be done.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram conceptually showing a cross-sectional structure of a soft magnetic thin film according to a first embodiment of the present invention. In FIG. 1, the soft magnetic thin film is composed of a base film 120 and a magnetic film 130 formed on a substrate 110. Here, any one of an Au film, an Ag film, an Al film, and a Ru film is used as the base film 120, and an Fe—Co—Al—O magnetic film is used as the magnetic film 130. As the substrate 110, a silicon wafer with a surface oxide film, Corning 7059 (trademark), alumina titanium carbide, or the like can be used. Note that a Ni—Fe film, a Ta film, a W film, an Mg film, a Cr film, a Ti film, a Zr film, a V film, an Hf film, or the like may be used as the base film 120 in addition to the above.

  Below, the manufacturing method of the soft-magnetic thin film which concerns on the 1st Embodiment of this invention is demonstrated.

For film formation, US IonTech. A hollow cathode type ion source manufactured by KK was used. The target was (Fe ₇₅ Co ₂₅ ) ₉₉ (Al ₂ O ₃ ) ₁ [at. %] Was used, and the inside of the apparatus was evacuated to 2 × 10 ⁻⁸ Torr or less, then the beam voltage was set to 1200 V, the beam current was set to 120 mA, and the krypton gas pressure was introduced to 0.8 × 10 ⁻⁴ Torr. A film was formed. A substrate used for film formation was set in parallel with the target and rotated at 5 revolutions per minute. A film was formed while a magnet was placed on the substrate and a magnetic field of 150 Oe was applied to the substrate. The thickness of the deposited film was 10 to 600 nm, and after the film formation, heat treatment was performed at 250 to 500 ° C. for 1 hour while applying a magnetic field of 1 kOe in a vacuum of 5 × 10 ⁻⁷ Torr or less.

The saturation magnetic flux density Bs and coercive force Hc of the produced soft magnetic thin film were measured using a vibrating sample magnetometer. In the present embodiment, the saturation magnetic flux density Bs is evaluated by the magnetic flux density B ₂₅₀ in the magnetic field ₂₅₀ Oe. The high-frequency magnetic permeability was measured as a complex magnetic permeability μ′−jμ ″ (μ ′ real part, μ ″ imaginary part) at 10 MHz to 2 GHz using a permeance meter. The above magnetic characteristics were measured in the direction perpendicular to the easy axis direction, that is, the hard axis direction.

  FIG. 2 is a diagram showing manufacturing information and various characteristics of Examples 1 to 26 of the soft magnetic thin film according to the first embodiment of the present invention. FIG. 3 is a diagram showing various characteristics of Comparative Examples 27 to 46 with respect to the example of the soft magnetic thin film. Here, the film thickness of the Fe—Co—Al—O thin film in the soft magnetic thin film is 100 nm. 2 and 3, the number shown in the right column in the “undercoat film” column is the film thickness of the undercoat film, and its unit is nm. The numerical value shown as μ′300 MHz is the value of the real part μ ′ of the complex permeability at 300 MHz. Further, the symbol “-” in FIGS. 2 and 3 indicates that measurement is impossible, and the description “none” in the column “heat treatment temperature” indicates that there is no heat treatment.

Based on the results shown in FIGS. 2 and 3, the following facts are generally shown.
(1) By using any one of an Au film, an Ag film, an Al film, and a Ru film as a base film having a film thickness of 0.5 nm to 5 nm, the Fe—Co—Al—O thin film has a B ₂₅₀ > 22 kG, Hc Properties of <6.0 Oe, fr> 1.6 GHz are obtained without heat treatment (see Examples 1-15).
(2) For an Fe—Co—Al—O thin film in which any one of an Au film, an Ag film, an Al film, and a Ru film is used as a base film having a film thickness of 0.5 nm to 5 nm, a temperature of 250 ° C. to 420 ° C. By performing the heat treatment, Hc decreases to 3.5 Oe or less, and μ′300 MHz increases to 1000 or more (see Examples 16 to 20, 22 to 26).
(3) By using a Ni—Fe film with a thickness of 2 nm as a base film, the Fe—Co—Al—O thin film has characteristics of B ₂₅₀ = 22 kG, Hc = 4.6 Oe, fr = 1.7 GHz without heat treatment. Is obtained (see Comparative Example 29).
(4) By performing a heat treatment at 250 ° C. to 420 ° C. on an Fe—Co—Al—O thin film having a Ni—Fe film with a thickness of 2 nm as a base film, Hc is reduced to 2.5 Oe or less, μ′300 MHz increases to 850 or more (see Comparative Examples 30 to 34).
(5) The Fe—Co—Al—O thin film using any one of Ta, Mg, W, Cr, Ti, Zr, V, and Hf as a base film has a large Hc of 25 Oe or more although Hc is reduced by heat treatment ( Comparative Examples 27, 28, 35-48).

  From the above, it is clear that when any one of the Au film, the Ag film, the Al film, and the Ru film is used as the base film, the soft magnetic characteristics are improved like the Ni—Fe thin film.

  FIG. 4 is a diagram showing the film thickness dependence of the Ag film of the characteristics of the soft magnetic thin film according to the first embodiment of the present invention. The Ag film thickness dependence shown in FIG. 4 is that the film thickness of the Fe—Co—Al—O thin film constituting the soft magnetic thin film is 100 nm. As shown in FIG. 4, by depositing an Ag thin film of 0.5 nm or more, the magnetic characteristics of the Fe—Co—Al—O thin film are greatly improved, and soft magnetic characteristics such as Hc <6 Oe, μ′300 MHz> 430 are obtained. It turns out that it is obtained. Note that the saturation magnetic flux density Bs of the Fe—Co—Al—O thin film using the Ag thin film as a base film was 23 kG or more, and the resonance frequency fr was 1.6 GHz or more.

  FIG. 5 is a diagram showing the characteristics after the sample having the characteristics shown in FIG. 4 is heat-treated at 350 ° C. for 1 hour. 4 and 5, the soft magnetic characteristics are improved by heat treatment at 350 ° C. for 1 hour, and Hc <2.2 Oe, μ′300 MHz> 1170 when an Ag underlayer having a thickness of 0.5 nm to 5 nm is used. It can be seen that the following characteristics can be obtained. Note that the saturation magnetic flux density Bs after heat treatment of the Fe—Co—Al—O thin film using the Ag thin film as a base film was 23 kG or more, and the resonance frequency fr was 1.8 GHz or more.

6 is a diagram showing the frequency characteristics of the complex permeability μ′−jμ ″ of the embodiment 20 of the present invention shown in FIG. 2. The complex permeability shown in FIG. 6 applies a magnetic field of ₁ mOe _0-p. The real part μ ′ of the complex permeability is in the range of 1000 to 1500 at a frequency of 10 MHz to 1.5 GHz, and the frequency at which the imaginary part μ ″ is a maximum, that is, the ferromagnetic resonance frequency is It can be seen that the frequency is about 1.7 GHz.

  As described above, the soft magnetic thin film and the manufacturing method thereof according to the first embodiment of the present invention use any one of an Au film, an Ag film, an Al film, and a Ru film as a base film. Even when a nonmagnetic underlayer film is used, it is possible to realize the characteristics that the saturation magnetic flux density Bs is 23 kG or more and the resonance frequency fr is 1 GHz or more.

  Further, by setting the thickness of the base film of any one of the Au film, the Ag film, the Al film, and the Ru film to 0.5 nm to 5 nm, the soft magnetic characteristics of the soft magnetic thin film can be improved.

  Furthermore, the soft magnetic thin film of the present invention is improved in soft magnetic properties by performing heat treatment within a temperature range from 250 ° C. to 420 ° C., and has heat resistance to a processing temperature during the head manufacturing process, for example, about 280 ° C. .

(Second Embodiment)
As shown in FIG. 7A, when the magnetic film 130 is formed of a single-layer magnetic film, a magnetic flux loop is formed in the plane of the magnetic film 130 so as to minimize magnetic flux leakage, and the magnetic film Magnetic domains having different magnetization directions 701 are formed at the ends of the first and second electrodes. In particular, when the size of the magnetic film is reduced and the width and thickness of the magnetic film are in the same order, the demagnetizing field, that is, the shape magnetic anisotropy, becomes a dominant factor that determines the magnetic characteristics.

  In such a case, the non-magnetic intermediate layer 702 is formed by making the magnetic film 130 a multi-layer structure in which any one of an Au film, an Ag film, an Al film, and a Ru film is the intermediate layer 702. At the ends of the two layers of the Fe—Co—Al—O magnetic films 703a and 703b adjacent to each other, the magnetization directions are opposite to each other and magnetostatically coupled, thereby reducing leakage magnetic flux, that is, demagnetizing field energy. This is possible (FIG. 7B). As described above, in the multilayer film, the magnetic domain structure is simplified, and the region having magnetization parallel to the easy axis is greatly increased. In general, a multilayer film has higher magnetic permeability than a single layer film, and has excellent frequency characteristics.

  The easy axis direction of magnetization of the soft magnetic thin film of the present invention is parallel to the magnetic field application direction during film formation or the magnetic field application direction during heat treatment. Therefore, the easy magnetization axis direction can be set to a desired direction. In the sample of Example 26, a magnetic field was set in a direction orthogonal to the easy magnetization axis direction during film formation and heat treatment was performed, and the easy magnetization axis direction was rotated 90 degrees. In addition, as the temperature of the heat treatment in the magnetic field application, the heat treatment temperature shown in the first embodiment of the present invention, that is, a temperature within a temperature range from 250 ° C. to 420 ° C. can be used.

Also in the sample of Example 26 described above, characteristics of B ₂₅₀ = 23.5 kG, Hc = 2.8 Oe, fr = 1.7 GHz are obtained. Having such characteristics is very useful when the present invention is applied to a magnetic head. Hereinafter, the perpendicular magnetic recording head conceptually shown in FIG. 8 will be described as an example. In the perpendicular magnetic recording head shown in FIG. 8, a magnetic circuit is composed of the perpendicular recording medium 801, the return yoke 803, and the recording magnetic pole 804, and the magnetization 802 is recorded on the perpendicular recording medium 801. Here, by making the track width direction indicated by W in FIG. 8 parallel to the easy axis of magnetization, the magnetic field intensity from the recording magnetic pole 804 can be increased, and the recording sensitivity to the perpendicular recording medium 801 can be improved. It becomes.

  As described above, the soft magnetic thin film, the manufacturing method thereof, and the magnetic head using the soft magnetic thin film according to the second embodiment of the present invention include any one of an Au film, an Ag film, an Al film, and a Ru film. By using such a non-magnetic film as an intermediate layer, it becomes possible to control the magnetic domain, which is impossible with a Ni-Fe film.

  In addition, the multilayer film of the present invention reduces leakage magnetic flux at the end of adjacent magnetic films because any of Au, Ag, Al, and Ru, which are elements constituting the intermediate layer, is a non-magnetic material. And problems due to the magnetic domain structure such as a decrease in magnetic permeability and generation of noise can be avoided.

  In addition, the soft magnetic thin film of the present invention can have its easy axis direction set to a desired direction depending on the direction of the magnetic field applied during film formation or heat treatment. As a result, when a soft magnetic thin film is used for the magnetic pole of a perpendicular magnetic head, the magnetic field intensity from the recording magnetic pole can be improved by making the easy axis direction parallel to the track width direction, and the recording sensitivity to the perpendicular medium can be improved. It becomes possible to raise.

It is a figure which shows notionally the cross-section of the soft-magnetic thin film which concerns on the 1st Embodiment of this invention. It is a figure which shows the manufacture information and the various characteristics of the Example etc. of the soft-magnetic thin film based on the 1st Embodiment of this invention. It is a figure which shows the manufacture information and its various characteristics, such as a comparative example of the soft-magnetic thin film which concerns on the 1st Embodiment of this invention. It is a figure which shows the film thickness dependency of the Ag film | membrane of the characteristic of the soft-magnetic thin film which concerns on the 1st Embodiment of this invention. It is a figure which shows the characteristic after heat-processing the sample which has the characteristic shown in FIG. 4 at 350 degreeC for 1 hour. It is a figure which shows the frequency characteristic of the complex magnetic permeability (micro | micron | mu) '-jmicro "of Example 20 of this invention shown in FIG. It is a figure for demonstrating the conceptual structure of the magnetic film 130 which concerns on the 2nd Embodiment of this invention, and its effect. It is a figure which shows the notional structure of a perpendicular magnetic recording head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 110 Substrate 120 Base film 130 Magnetic film 701 Direction of magnetization 702 Intermediate layer 703a, 703b Fe-Co-Al-O magnetic film 801 Perpendicular recording medium 802 Magnetization 803 Return yoke 804 Recording magnetic pole

Claims (9)

A soft magnetic thin film characterized in that an Au film is formed as a base film on a substrate, and an Fe-Co-Al-O magnetic film is formed on the Au film. A soft magnetic thin film characterized in that an Ag film is formed as a base film on a substrate, and an Fe-Co-Al-O magnetic film is formed on the Ag film. A soft magnetic thin film characterized in that an Al film is formed as a base film on a substrate, and an Fe-Co-Al-O magnetic film is formed on the Al film. A soft magnetic thin film characterized in that a Ru film is formed as a base film on a substrate, and an Fe-Co-Al-O magnetic film is formed on the Ru film. 5. The soft magnetic thin film according to claim 1, wherein the base film has a thickness in a range of not less than 0.5 nm and not more than 5 nm. 2. The Fe—Co—Al—O magnetic film, wherein a plurality of layers are separated and stacked with any one of an Au film, an Ag film, an Al film, and a Ru film as an intermediate layer. The soft magnetic thin film according to claim 5. The soft magnetic thin film according to any one of claims 1 to 6, wherein the soft magnetic thin film is manufactured by heat treatment in a magnetic field within a temperature range of 250 ° C to 420 ° C. 8. A magnetic head using the soft magnetic thin film according to claim 1 as the soft magnetic thin film. A method for producing a soft magnetic thin film, comprising subjecting the soft magnetic film according to any one of claims 1 to 6 to heat treatment in a magnetic field within a temperature range of 250 ° C to 420 ° C.

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