JP3340420B2 - Perpendicular magnetic recording medium and magnetic storage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic recording medium and a magnetic storage device which are suitable for ultra-high-density magnetic recording and have low reproduction noise and excellent recording magnetization stability.

[0002]

2. Description of the Related Art Currently, practically used magnetic recording systems include an N-pole and an N-pole, which are parallel to the surface of a magnetic recording medium and are magnetic poles.
This is an in-plane magnetic recording system in which magnetic recording is performed by magnetizing the poles, the S pole, and the S pole in a direction in which they face each other. In order to improve the linear recording density in the longitudinal magnetic recording method, the product Br · t of the residual magnetization Br and the magnetic film thickness t of the magnetic film as the recording medium is reduced to reduce the effect of the demagnetizing field during recording. , It is necessary to increase the coercive force. Further, in order to reduce the medium noise generated from the magnetization transition, it is necessary to orient the easy axis of the magnetic film parallel to the substrate surface and to control the crystal grain size.

As a magnetic film for longitudinal magnetic recording, Co is used as a main component and Cr, Ta, Pt, Rh, Pd, T
A Co alloy thin film to which i, Ni, Nb, Hf or the like is added is used. As the Co alloy constituting the magnetic thin film, a material having a hexagonal close-packed lattice structure (hereinafter, referred to as an hcp structure) is mainly used. The c axis of the crystal has an easy axis in the <00.1> direction, and the easy axis is oriented in the in-plane direction. In order to control the crystal orientation and grain size of the magnetic thin film, an underlayer for structure control is formed between the substrate and the magnetic film. The base layer is mainly composed of Cr, and Ti, Mo, V, W, P
A material to which t, Pd, or the like is added is used. The magnetic thin film is formed by a vacuum evaporation method or a sputtering method. When a glass substrate or the like is used, a medium in which a precoat of a Ni-Al alloy or a Co-Cr-Zr alloy is formed under the Cr alloy underlayer to improve the crystal orientation and magnetic properties of the in-plane magnetized film is used. Can be As described above, in order to reduce medium noise and improve linear recording density in longitudinal magnetic recording,
It is necessary to reduce the product of the residual magnetization Br of the magnetic film and the magnetic film thickness t. For this purpose, it is necessary to reduce the film thickness of the magnetic film to 20 nm or less and to reduce the crystal grain size to 10 to 15 nm. is there. However, such a medium in which the magnetic crystal grains are made fine has a very serious problem that the recording magnetization decreases due to thermal fluctuation, which is an obstacle to high-density recording.

On the other hand, the perpendicular magnetic recording system is a magnetic recording system in which magnetic domains are formed perpendicularly to the recording medium surface so that adjacent recording bits are antiparallel to each other. There is an advantage that the smaller the recording density is, the more easily the magnetization can be stably maintained as the recording density is high. This is one of the effective means of the high-density magnetic recording. For high-density recording by in-plane magnetic recording, as described above, it is necessary to reduce the thickness of the magnetic film to 20 nm or less and to make the magnetic crystal grain size finer and more uniform. Therefore, there is a problem that the recorded magnetization disappears. On the other hand, perpendicular magnetic recording has the advantage that the magnetic film thickness can be made larger than in-plane magnetic recording, and that the recorded magnetization can be stably maintained. In order to improve linear recording density by perpendicular magnetic recording, it is necessary to reduce medium noise generated from magnetic domains having irregular structures formed inside recording bits and in a magnetization transition region. To this end, it is necessary to align the easy axis of the magnetic film perpendicular to the substrate surface, reduce the orientation dispersion of the easy axis, and control the crystal grain size.

The perpendicular magnetization film has Co as a main component,
This includes Cr, Ta, Pt, Rh, Pd, Ti, Ni, N
For example, a Co alloy thin film to which b, Hf, or the like is added, a Te—Fe—Co amorphous material in which a rare earth element is added to Co, or a multilayer film material of Co and Pt or Pd is used.
As the Co alloy constituting the magnetic thin film, mainly hcp
Use structural materials. The Co alloy thin film has the c
The axis has an easy axis in the <00.1> direction, and the easy axis is oriented in a direction perpendicular to the recording medium surface. The magnetic thin film is formed by a vacuum evaporation method or a sputtering method. In order to improve the linear recording density and reproduction output when performing magnetic recording, reduce the reproduction noise and improve the magnetic recording characteristics, improve the c-axis vertical orientation of the Co alloy thin film and increase the crystal grain size. Therefore, improvement measures such as forming an underlayer for structure control between the substrate and the magnetic film have been conventionally taken.

[0006] The perpendicular magnetic recording medium includes a single-layer perpendicular magnetic recording medium having a perpendicular magnetization film formed on a substrate via a structure control layer, and a soft magnetic film formed on a substrate, and a structure control layer formed thereon. There is a two-layer perpendicular magnetic recording medium in which a perpendicular magnetization film is formed through the medium. In the former case, the main cause of the medium noise is a magnetic domain having an irregular structure formed inside the recording bit and in the magnetization transition region due to the influence of the demagnetizing field. On the other hand, in the case of the latter two-layer perpendicular magnetic recording medium, the medium noise is caused by irregular magnetic domains formed in the recording bit and in the magnetization transition region, as well as the soft magnetic film provided under the perpendicular magnetization film. It is also caused by disturbance of the magnetic domain structure of the magnetic layer.

As a method for controlling the magnetic domain structure of the soft magnetic film, for example, as described in Japanese Patent Application Laid-Open No. H11-191217, "Method for Manufacturing a Perpendicular Magnetic Recording Medium", easy magnetic domains are formed in the in-plane direction below the soft magnetic film. A method for forming an oriented hard magnetic film has been proposed. According to this method, the effect of reducing the change of the magnetic domain structure of the soft magnetic film due to an external magnetic field is recognized to some extent, but the hard magnetic film is formed by directly contacting the in-plane oriented hard magnetic film below the soft magnetic film. The magnetic domain structure of the film is transferred to the soft magnetic film thereon, and as a result, there is a problem that noise generated from the soft magnetic film is included in the reproduction signal of the perpendicular magnetization film and causes an obstacle to high density recording.

[0008]

In order to realize ultra-high-density magnetic recording with a perpendicular magnetic recording medium, especially a two-layer perpendicular magnetic recording medium, it is necessary to improve the linear recording density and to improve the noise included in the reproduced signal, especially the medium. It is important to reduce the medium noise caused by the fine structure and to keep the recording magnetization stable. The present invention, based on recognition of such a problem, solves the drawbacks of the prior art, and has excellent low noise characteristics and stable recording magnetization, and has a perpendicular magnetic recording medium and a magnetic recording medium suitable for ultra-high density magnetic recording. It is an object to provide a storage device.

[0009]

Means for Solving the Problems The present inventors have examined in detail the factors which hinder the stability of the recording magnetization and the causes of the medium noise in a perpendicular magnetic recording medium having a backing magnetic layer, and as a result, It was found that the magnetic domain structure affected the leakage magnetic field distribution on the surface of the perpendicular magnetic recording medium during magnetic recording, increased the medium noise, and hindered the stability of recording magnetization.

In a perpendicular magnetic recording medium having a backing magnetic layer, the backing magnetic layer serves as (1) a role of a return path for improving the recording efficiency of a recording head during perpendicular magnetic recording;
(2) It is conventionally used mainly for the purpose of improving the reproduction signal output from the perpendicular magnetization film. In the present invention, the relationship between the structure of the backing magnetic layer and the magnetic domain structure on the surface, and the relationship between the magnetic domain structure due to the interaction between the backing magnetic layer and the perpendicular magnetization film, particularly the crystal orientation and the magnetic domain structure of the hard magnetic film contained in the backing magnetic layer Was systematically examined, and a suitable means for reducing the medium noise of the perpendicular magnetic recording medium was found.

In the present invention, by controlling the structure of the backing magnetic layer formed below the perpendicular magnetization film in addition to controlling the crystal orientation and crystal grain size of the perpendicular magnetization film, the magnetic domain structure on the surface of the backing magnetic layer can be particularly improved. The object is achieved by controlling and reducing the magnetic domains of the irregular structure formed on the surface of the perpendicular magnetization film when performing magnetic recording. Specifically, in a perpendicular magnetic recording medium in which a backing magnetic layer, a perpendicular magnetic film, and a protective film are formed in this order on a substrate, the backing magnetic layer has a structure in which magnetic films having different compositions or coercive forces are laminated, and By systematically examining the relationship between the structure and the magnetic domain structure on the surface, it is possible to provide a perpendicular magnetic recording medium suitable for ultra-high-density magnetic recording with small medium noise and excellent recording magnetization stability.

That is, in the perpendicular magnetic recording medium according to the present invention, in a perpendicular magnetic recording medium in which a perpendicular magnetic film is provided on a substrate via a backing magnetic layer, the backing magnetic layer has an easy axis of magnetization formed on the side close to the substrate. It is characterized by including a vertically oriented hard magnetic film and a soft magnetic film formed on the hard magnetic film.

The hard magnetic film has a coercive force of 1 kOe or more,
The soft magnetic film can be an amorphous soft magnetic film having a coercive force of 1 Oe or less. The hard magnetic film has a coercive force of 1 kOe or more, and the soft magnetic film has a laminated structure in which an amorphous soft magnetic film is formed on a polycrystalline soft magnetic film and has a coercive force of 1 Oe or less. can do.

The amorphous soft magnetic film is made of a Co-Nb-Zr-based amorphous alloy, a Co-Mo-Zr-based amorphous alloy, or a Co-WZ
r-based amorphous alloy, Co-Ta-Zr-based amorphous alloy, Co
-Ni-Zr-based amorphous alloy, the polycrystalline soft magnetic film may be made of Fe-Al-
Si-M alloy (M: Cr, Ti), Fe-Ta-CM
Alloy (M: Al, Cr), Fe-Hf-CM alloy (M: Al, Cr), Fe-Ta-NM alloy (M: A
1, Cr) and Ni-Fe-M alloy (M: Nb, Mo), and the hard magnetic film contains Co as a main component and contains Cr, Pt, Ta, and Hf. ,
It can be composed of an alloy to which any of Sm is added.
Here, the notation (M: a, b) indicates that M is a or b. A film thickness of 1 to 10 between the backing magnetic layer and the perpendicular magnetization film
It is preferable to include a nonmagnetic structure control layer having a thickness of nm.

A magnetic storage device according to the present invention has a magnetic recording medium, a driving unit for driving the magnetic recording medium, a magnetic head including a recording unit and a reproducing unit, and a magnetic head relatively to the magnetic recording medium. Magnetic head driving means for moving,
A magnetic storage device comprising a signal processing means for processing a recording signal and a reproduction signal of a magnetic head, wherein the above-described perpendicular magnetic recording medium is used as a magnetic recording medium. The recording section of the magnetic head can be constituted by a ring-type or single-pole type magnetic recording head. The reproducing section of the magnetic head can be constituted by a magneto-resistive, spin-valve or magnetic tunnel type signal reproducing head.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. In the figure, the portions denoted by the same reference numerals indicate portions having the same performance characteristics.

[Embodiment 1] A perpendicular magnetic recording medium according to the present invention can be provided with a recording layer on one or both sides of a substrate surface. FIG. 1 shows an example of a basic structure of a perpendicular magnetic recording medium according to the present invention. FIG. The perpendicular magnetic recording medium shown in FIG. 1 has a backing magnetic layer 12, a perpendicular magnetic film structure control layer 15, a perpendicular magnetic film 16, and a protective film 17 on a substrate 11. The backing magnetic layer 12 has a laminated structure composed of a hard magnetic film 13 having a high coercive force and a soft magnetic film 14.
The hard magnetic film 13 having a high coercive force has a role of preventing the magnetic domain structure of the soft magnetic film 14 formed thereon from being changed by an external magnetic field.
Greater than 4 and in the range of 20-4000 Oe, preferably 1
The range of 000 to 4000 Oe is good. For the hard magnetic film 13 having a high coercive force, a material whose easy axis of magnetization is oriented in a direction perpendicular to the substrate surface is used. The coercive force of the soft magnetic film 14 is preferably 20 Oe or less, and more preferably 1 Oe or less. Further, the soft magnetic film 14 may be formed by laminating materials having different coercive forces.

Using a high vacuum DC magnetron sputtering apparatus, a medium having a sectional structure shown in FIG. 1 was produced. The washed glass substrate 11 was set in a sputtering apparatus, and subsequently, the substrate 11 was heated to about 300 ° C. As the hard magnetic film 13 having a high coercive force, a sample having an easy axis of magnetization oriented in a direction perpendicular to the substrate surface was prepared. First, a precoat layer was formed on the substrate. The precoat layer is used to promote the crystal orientation of the vertically oriented hard magnetic film 13 formed thereon, and includes Ti, Hf, Ti—Cr alloy, Hf—Cr alloy, non-magnetic Co—Cr alloy, An amorphous material such as Si, Ge, and C can be used. In this embodiment, the film thickness is 30.
nm Ti-10 at% Cr alloy was used.

On this pre-coat layer, a non-magnetic Co-35 at% Cr alloy film having a film thickness of 20 nm is interposed to form a film having a film thickness of 25 nm.
The hard magnetic film 13 whose easy axis of magnetization was vertically oriented was formed.
The hard magnetic film 13 contains Co as a main component,
r, Ta, Pt, Rh, Pd, Ti, Ni, Nb, Hf
A Co alloy thin film to which Co or the like is added or a material to which Co is added a rare earth element can be used. In this embodiment, Co-18 at% Cr-14 at% Pt-3 at% Ta is used.
An example using an alloy will be described. The coercive force in the direction perpendicular to the film surface of the hard magnetic film 13 was 3000 Oe, and the squareness ratio (SQ = the ratio of residual magnetization to saturation magnetization) was 0.82. Subsequently, a Co-10 at% T is formed on the hard magnetic film 13 as a soft magnetic film 14.
An a-5 at% Zr amorphous alloy film was formed. Soft magnetic film 1
The coercive force of No. 4 was 0.3 Oe, and the initial magnetic permeability was 500.
In order to examine the effect of the hard magnetic film 13 on the magnetic domain structure of the soft magnetic film 14, a sample was manufactured in which the thickness of the soft magnetic film was changed in the range of 0 to 400 nm.

A structure control layer 15 is formed on the soft magnetic film 14, and a 20 nm-thick perpendicular magnetization film 16 and a 5n-thick
m protective films 17 were sequentially formed. The structure control layer 15 has a role of improving the crystal orientation of the perpendicular magnetization film 16 formed thereon and a role of controlling the crystal grain size.
-Cr alloy, Hf-Cr alloy, or non-magnetic Co-
An hcp structure material such as a Cr alloy or an amorphous material such as Si, Ge, or C can be used. Here, an example in which a Ti-10 at% Cr alloy having a thickness of 5 nm is used as the structure control layer 15 will be described. As the perpendicular magnetization film 16, Co is used.
An alloy of -18 at% Cr-12 at% Pt-3 at% Ta was used, and carbon was used as the protective film 17. The coercive force of the perpendicular magnetization film 16 in the direction perpendicular to the film surface was 3100 Oe, and the squareness ratio was 0.9.

For comparison, a sample was prepared as the hard magnetic film 13 in which the axis of easy magnetization was oriented parallel to the substrate surface. First, a Ni-5 layer having a thickness of 50 nm was formed on the substrate as a precoat layer.
A 0 at% Al alloy film is formed, and a 20 nm-thick film is formed thereon as an underlayer for controlling the crystal orientation of the hard magnetic film 13 having a high coercive force.
Was formed. This Cr film was oriented in the <110> or <100> direction. In order to improve the crystal orientation of the hard magnetic film 13, a CrTi film is formed on the Cr film.
_x (x = 10 to 20 at%) and CrMo _x (x = 10 to 20 at%)
20 at%) or CrV _x (x = 10 to 20 at)
%) It is also possible to form and use a film.

On this underlayer, a hard magnetic film 13 having a high coercive force is formed.
Co-18 at% Cr-14 at 25 nm in thickness
% Pt-3 at% Ta thin film was formed. This hard magnetic film 1
In No. 3, the c-axis of the hcp structure was oriented almost parallel to the substrate surface. The coercive force in the in-plane direction of the hard magnetic film 13 is 2500O.
e, squareness ratio (SQ = ratio of residual magnetization to saturation magnetization) is 0.8
It was 2. Subsequently, a Co-10 at% Ta-5 at% Zr amorphous alloy film was formed as a soft magnetic film 14 on the hard magnetic film 13. In order to investigate the effect of the hard magnetic film 13 on the magnetic domain structure of the soft magnetic film 14, the thickness of the soft magnetic film was set to 0.
Samples varied in the range of ４００400 nm were prepared. A structure control layer 15 was formed on the soft magnetic film 14, and a 20 nm-thick perpendicular magnetic film 16 and a 5 nm-thick protective film 17 were sequentially formed thereon. Co-18at is used as the perpendicular magnetization film 16.
% Cr-12 at% Pt-3 at% Ta alloy was used, and carbon was used as the protective film 17. The coercive force of the perpendicular magnetization film 16 in the direction perpendicular to the film surface is 3080 Oe, and the squareness ratio is 0.8.
Nine.

FIG. 2 shows the structure of a magnetic domain structure comparison test sample. (A) to (D) in the figure indicate that the film was formed up to the height position, (A) is a sample formed up to the hard magnetic film 13, (B) is on the hard magnetic film 13 Thickness 40nm
Sample on which the Co-Ta-Zr soft magnetic film 14 was formed,
(C) shows a 400 nm thick Co-T film on the hard magnetic film 13.
The sample on which the a-Zr soft magnetic film 14 was formed, (d) shows a structure control layer 15 and a 20 nm thick Co on the soft magnetic film 14.
This is a sample in which a -18 at% Cr-12 at% Pt-3 at% Ta alloy perpendicular magnetization film 16 and a 5 nm-thick carbon protective film 17 are sequentially formed. As the hard magnetic film 13, a medium of the present invention in which the easy axis was oriented in the direction perpendicular to the film surface and a comparative sample in which the easy axis was oriented parallel to the film surface were prepared.

FIG. 3 shows a comparison of the magnetic domain structure in the remanent magnetization state of the test sample. The domain structure was measured with a magnetic force microscope. In the figure, the column (a) shows the magnetic domain structure of the medium according to the present invention, and the column (b) shows the magnetic domain structure of the comparative medium. (A) of the row of (a) and the row of (b)
(D) correspond to the medium configuration shown in FIG. For example, (a) shows the surface of the hard magnetic film 13 (soft magnetic film thickness 0 nm)
Similarly, (b) shows the magnetic domain structure on the surface of the soft magnetic film having a thickness of 40 nm formed on the hard magnetic film 13, and (c) shows the magnetic domain structure formed on the hard magnetic film 13. Thickness 400
the magnetic domain structure on the surface of the soft magnetic film of
Shows the magnetic domain structure on the surface of each.

In this magnetic domain structure, disturbance of the magnetic domain structure is shown by light and dark contrast. In the figure, a region observed with black contrast is a magnetic domain having an irregular structure that causes medium noise. The smaller the size of the irregular magnetic domain and the smaller the signal generated from the magnetic domain, the smaller the noise. Hard magnetic film 13 vertically oriented as in the present invention
In the medium on which the soft magnetic film 14 is formed, the size of the irregular magnetic domain on the surface of the soft magnetic film is small as shown in FIGS. On the other hand, in the comparative medium (b) in which the soft magnetic film was formed on the in-plane oriented hard magnetic film, the size of the irregular magnetic domains on the surface of the soft magnetic film was large, and especially when reproduced by a magnetic head, the long-wavelength component Is a source of the noise signal.
Further, as can be seen from FIG. 3, in the comparative medium, the magnetic domain structure on the surface changes greatly with the soft magnetic film thickness. That is, when the soft magnetic film thickness is small, disturbance of the magnetic domain structure on the surface of the lower hard magnetic film is emphasized and appears. When the soft magnetic film thickness is large, a large magnetic domain tends to be easily formed on the surface. On the other hand, in the medium of the present invention, the dependence of the magnetic domain structure on the soft magnetic film thickness is small, the magnetic domain size is small, and the effect of reducing the medium noise is large.

The noise spectrum of a sample in which a perpendicular magnetization film was formed on the soft magnetic film, ie, the sample corresponding to FIG. 3D, was measured, and signals from the irregular magnetic domains were quantitatively compared. FIG. 4 shows the results. In FIG. 4, the horizontal axis represents the wavelength of the noise signal or the reciprocal of the wavelength, and the vertical axis represents the intensity of the noise signal as a relative value. In the figure, (a) shows the noise characteristic of the perpendicular magnetic recording medium according to the present invention, and (b) shows the noise characteristic of the comparative medium. When reproducing signals are compared in a state where the spacing between the medium and the magnetic head is constant, the noise signal decreases as the size of the irregular magnetic domain decreases due to the spacing loss and gap loss of the magnetic head. As is clear from the figure, the medium of the present invention has a smaller noise signal intensity in almost the entire wavelength region than the comparative medium.
In particular, the comparative medium has a large noise signal of a long wavelength component of a wavelength of 0.2 μm or more. That is, the medium for comparison contains a large amount of irregular magnetic domains of a large size in the medium, which means that medium noise is large. In the noise spectrum of FIG.
When the noise containing all wavelength components of 0.06 to 10 μm was compared between the medium of the present invention and the comparative medium, the medium of the present invention showed low noise characteristics at about 1 dB.

Here, Co-10 is used as the soft magnetic film 14.
Although an example using an at% Ta-5 at% Zr amorphous alloy film has been described, a Co-Nb-Zr-based amorphous alloy, Co-
Mo-Zr-based amorphous alloy, Co-W-Zr-based amorphous alloy, Co-Ta-Zr-based amorphous alloy, or Co-N
An i-Zr-based amorphous alloy may be used. It was confirmed by X-ray diffraction and TEM (transmission electron microscope) observation that these soft magnetic films were all films having an amorphous structure. Further, although an example using a glass substrate as the substrate 11 has been described, a Si disk substrate, a NiP-coated aluminum substrate, a carbon substrate, a polymer substrate, or the like may be used instead of the glass substrate. Further, as the hard magnetic film 13, Co-
Although the example using the 18 at% Cr-14 at% Pt-3 at% Ta thin film has been described, Co is used as a main component and Cr,
Another alloy to which any of Pt, Ta, Hf, and Sm is added may be used.

Embodiment 2 FIG. 5 is a schematic sectional view showing another example of a perpendicular magnetic recording medium according to the present invention. The perpendicular magnetic recording medium shown in FIG.
The structure is formed by laminating a structure control layer 15, a perpendicular magnetization film 16, and a protective film 17 of a perpendicular magnetization film. The backing magnetic layer 12 has a laminated structure composed of a hard magnetic film 13 having a high coercive force and a soft magnetic film 14. The soft magnetic film 14 is composed of two types of materials.

That is, the soft magnetic film 14 is composed of a polycrystalline soft magnetic film 14-1 formed below and an amorphous soft magnetic film 14-2 formed thereon. Polycrystalline soft magnetic film 14-
1 is, for example, an Fe-Al-Si-M alloy (M: Cr, T
i), Fe-Ta-CM alloy (M: Al, Cr), F
e-Hf-CM alloy (M: Al, Cr), Fe-Ta
-N-M alloy (M: Al, Cr) and Ni-Fe-M alloy (M: Nb, Mo). Amorphous soft magnetic film 14
-2 is, for example, a Co-Nb-Zr-based amorphous alloy, Co-
Mo-Zr-based amorphous alloy, Co-W-Zr-based amorphous alloy, Co-Ta-Zr-based amorphous alloy, Co-Ni-Zr
Selected from non-crystalline amorphous alloys. Amorphous soft magnetic film 14-
No. 2 has a role of preventing formation of micro magnetic domains on the surface of the soft magnetic film due to disorder of the crystal orientation of the polycrystalline soft magnetic film 14-1 formed as a lower layer. The lower polycrystalline soft magnetic film 14-1 has a role of promoting the magnetic domain fixing effect of the upper amorphous soft magnetic film 14-2 by magnetic interaction with the hard magnetic film 13. In this embodiment, the soft magnetic film 14
-1, Fe-8 at% Ta-12 at% C alloy film,
Co-4 at% Ta-9 at% as the soft magnetic film 14-2
An example using a Zr amorphous alloy film will be described.

Using a high vacuum DC magnetron sputtering apparatus, a perpendicular magnetic recording medium having a sectional structure shown in FIG. 5 was produced. The washed glass substrate 11 was set in a sputtering apparatus, and subsequently, the substrate 11 was heated to about 300 ° C. As the hard magnetic film 13 having a high coercive force, a sample having an easy axis of magnetization oriented in a direction perpendicular to the substrate surface was prepared. First, a 30 nm-thick Ti-10 at% Cr alloy pre-coat layer was formed on the substrate. On this pre-coat layer, a Co-16 at% Cr-14a having a 25 nm-thick film whose easy axis of magnetization is vertically oriented via a non-magnetic Co-35 at% Cr alloy film having a thickness of 20 nm.
A t% Pt-3 at% Ta alloy hard magnetic film 13 was formed.
The coercive force of the hard magnetic film 13 in the direction perpendicular to the film surface is 3300 Oe,
The squareness ratio (SQ = the ratio of residual magnetization to saturation magnetization) was 0.89.

Subsequently, the soft magnetic film 14-1 and the soft magnetic film 14-2 are formed on the hard magnetic film 13 as soft magnetic films 14.
Were sequentially formed. Fe-8at as the soft magnetic film 14-1
A Co-4 at% Ta-9 at% Zr amorphous alloy film was used as the% Ta-12 at% C alloy film and the soft magnetic film 14-2. The soft magnetic film 14 has a role as a return path of the recording head magnetic flux at the time of magnetic recording and a role of improving the output from the perpendicular magnetization film at the time of signal reproduction. In order to examine the effect of the thickness of the soft magnetic film 14-1 and the soft magnetic film 14-2, the total thickness of the soft magnetic film 14 was set to 400 nm, and the thickness of the soft magnetic film 14-2 was set to 0 to 400 nm. Samples varied in the range were prepared. The coercive force of the soft magnetic film 14 was 0.2 to 0.8 Oe, and the initial magnetic permeability was 200 to 800.

On the soft magnetic film 14, a 5-nm thick Ti-1
A structure control layer 15 made of a 0 at% Cr alloy was formed, and a 20 nm-thick perpendicular magnetic film 16 and a 5 nm-thick protective film 17 were sequentially formed thereon. As the perpendicular magnetization film 16, Co is used.
An alloy of -18 at% Cr-12 at% Pt-3 at% Ta was used, and carbon was used as the protective film 17. The coercive force of the perpendicular magnetization film 16 in the direction perpendicular to the film surface was 3150 Oe, and the squareness ratio was 0.91.

For comparison, a sample was prepared in which the axis of easy magnetization of the hard magnetic film 13 was oriented parallel to the substrate surface. First, a 50 nm-thick Ni-5 film was formed on the substrate 11 as a precoat layer.
A 0 at% Al alloy film is formed, and a 20 nm-thick film is formed thereon as an underlayer for controlling the crystal orientation of the hard magnetic film 13 having a high coercive force.
Was formed. This Cr film was oriented in the <110> or <100> direction. On this underlayer, Co-16a having a thickness of 25 nm was formed as a hard magnetic film 13 having a high coercive force.
A t% Cr-14at% Pt-3at% Ta alloy thin film was formed. In the hard magnetic film 13, the c-axis of the hcp structure was oriented substantially parallel to the substrate surface. The coercive force in the in-plane direction of the hard magnetic film 13 was 2800 Oe, and the squareness ratio (SQ = the ratio of residual magnetization to saturation magnetization) was 0.81.

Subsequently, a soft magnetic film 14 was formed on the hard magnetic film 13. The soft magnetic film 14 is formed by sequentially forming a soft magnetic film 14-1 and a soft magnetic film 14-2 on the hard magnetic film 13. Fe-8 at% Ta-12 as the soft magnetic film 14-1
Co-4at as at% C alloy film and soft magnetic film 14-2
% Ta-9 at% Zr amorphous alloy film was used. In order to examine the effect of the thickness of the soft magnetic film 14-1 and the soft magnetic film 14-2, the total thickness of the soft magnetic film 14 was set to 400 nm, and the thickness of the soft magnetic film 14-2 was set to 0 to 400 nm. Samples with varying ranges were made. The coercive force of the soft magnetic film 14 is 0.2 to
0.8 Oe, and the initial magnetic permeability was 200 to 800. A structure control layer 15 made of a Ti-10 at% Cr alloy having a thickness of 5 nm is formed on the soft magnetic film 14, and a 20 nm film thickness is formed thereon.
An m-perpendicular film 16 and a 5 nm-thick protective film 17 were sequentially formed. Co-18 at% Cr for the perpendicular magnetization film 16
Protective film 1 using -12 at% Pt-3 at% Ta alloy
7 was carbon. The coercive force of the perpendicular magnetization film 16 in the direction perpendicular to the film surface was 3100 Oe, and the squareness ratio was 0.90.

The effect of the crystal orientation of the hard magnetic film 13 on the surface magnetic domain structure of the soft magnetic film 14 was compared by observing the magnetic domain structure in a remanent magnetization state. FIG. 6 shows a magnetic domain structure observed with a magnetic force microscope. In FIG. 6, (a) shows the axial structure of the medium according to the present invention in which the easy axis of magnetization of the hard magnetic film 13 is oriented in the direction perpendicular to the film surface, and (b) shows the hard magnetic film 1.
3 shows the magnetic domain structure of a comparative medium in which the easy axis of magnetization 3 is oriented in the direction parallel to the film surface. In the same figure, (a), (b)
(A) shows the hard magnetic film 13 as shown by the arrow in FIG.
(B) is a magnetic domain structure on the surface of the soft magnetic film 14-2. Here, (b) shows the soft magnetic film 14 as an example.
The results when the film thickness of -1 is 360 nm and the film thickness of the soft magnetic film 14-2 is 40 nm are shown.

In this magnetic domain structure, disturbance of the magnetic domain structure is shown by light and dark contrast. In FIG. 6, the region observed with black contrast is a magnetic domain having an irregular structure that causes medium noise, and the smaller the size of the irregular structure magnetic domain and the smaller the signal generated from the magnetic domain,
Noise is small. In the medium (a) of the present invention in which a soft magnetic film is formed on a vertically oriented hard magnetic film, as shown in FIG. 6A, the size of the irregular magnetic domains on the surface of the hard magnetic film is small, and There is little disturbance of the magnetic domain structure on the surface of the magnetic film. On the other hand, in the comparative medium (b) in which the soft magnetic film was formed on the in-plane oriented hard magnetic film, the size of the irregular magnetic domains on the surface of the hard magnetic film was large, and the magnetic domains with stripes were formed on the soft magnetic film surface. Are formed and large disturbance of the magnetic domain structure is observed. This becomes a source of a noise signal particularly of a long wavelength component when reproduced by a magnetic head.

FIG. 7 shows the relationship between the thickness of the soft magnetic film 14-2 and the medium noise in the perpendicular magnetic recording medium according to the present invention and the comparative medium whose sectional structures are shown in FIG. A single-pole head (with a track width of 1.2)
perpendicular magnetic recording with a magnetic pole saturation magnetic flux density of 1.6 Tesla) and a GMR head (giant magnetoresistive head, track width 0.8 μm, gap length 0.12 μm)
Played with. The spacing between the medium and the head during magnetic recording / reproducing was set to about 16 nm. The relationship between the recording current and the overwrite characteristics (recording a signal of 45 kFCI on 254 kFCI) was measured, and the overwrite S / N was 35 dB.
Magnetic recording was performed with a recording current that ensures the above. After the magnetic recording, the medium noise was reduced to 0 to 4 using the GMR head.
A noise spectrum in the range of 0 MHz was measured, and the integrated intensity in this range was measured. The medium noise in FIG. 7 is shown as a relative value.

As is apparent from FIG. 7, the medium noise can be reduced by forming the amorphous soft magnetic film 14-2 on the polycrystalline soft magnetic film 14-1. Further, as compared with the comparative medium in which the easy axis of magnetization is in-plane oriented as the hard magnetic film 13, the medium of the present invention in which the easy axis of hard magnetic film 13 is oriented perpendicular to the film surface is excellent in any thickness. Noise characteristics were obtained.

FIG. 8 shows that the thickness of the soft magnetic film 14-1 is 360
5 shows the results of spectrum analyzer measurement of medium noise after DC erasing for the medium of the present invention and the comparative medium in which the thickness of the soft magnetic film 14-2 was 40 nm. The medium for comparison has a larger noise signal intensity especially for a long wavelength component of 25 MHz or less than the medium of the present invention. As shown in the magnetic domain structure on the surface of the soft magnetic film in FIG. 6, a magnetic domain structure in the form of stripes is formed on the surface of the soft magnetic film of the comparative medium. It is considered that the influence of the magnetic domain structure of the perpendicular magnetization film formed in the above-mentioned method increases the medium noise of the long wavelength component.

Embodiment 3 FIG. 9 is a schematic diagram of a magnetic storage device according to the present invention. The magnetic storage device includes a magnetic disk 31, a motor for rotating the magnetic disk 31, a magnetic head 32 for recording and reproduction, a suspension 33 for supporting the magnetic head 32, and an actuator for driving the magnetic head 32 relative to the magnetic disk. 34, a voice coil motor 35, a recording / reproducing circuit 36 for processing recording signals and reproducing signals, a magnetic head positioning circuit 37, an interface control circuit 38, and the like. Magnetic disk 31
Is composed of the perpendicular magnetic recording medium described in the first embodiment or the second embodiment, and the protective film is covered with a lubricating film. The magnetic head 32 includes a magnetic recording head provided on a slider and a reproducing head composed of a magnetoresistive, giant magnetoresistive, spin-valve or magnetic tunnel element for reproducing signals. .
The gap length of the magnetic head for reproducing the recording signal is set to 0.25 μm or less, preferably 0.08 to 0.15 μm in order to obtain a high-resolution reproduction signal. As a magnetic recording head, either a single pole type head or a ring type head may be used. The track width of the reproducing head is made narrower than the track width of the recording head magnetic pole to reduce reproduction noise generated from both ends of the recording track.

The magnetic head 32 is supported by the suspension 33. Using this apparatus, the first and second embodiments were used.
The medium noise characteristics and the recording / reproducing characteristics of the perpendicular magnetic recording medium described in the above section were evaluated. The perpendicular magnetic recording medium of the present invention, the output half-line recording density _{D 5} 0: _280kFCI, medium in the density Noise: 8μVrms / μVpp, Error rate: ^{10 -6} or less dense characteristic was obtained. In the above-described embodiment, the description has been made by giving examples of the perpendicular magnetization film, the structure control layer, the soft magnetic film, and the hard magnetic film. However, the same applies when any of the other materials described in the embodiment is used in combination. Needless to say, the effect is obtained.

[0042]

According to the present invention, the formation of striped magnetic domains on the surface of the soft magnetic film which causes medium noise is suppressed, and the size of the irregular magnetic domains on the surface of the perpendicular magnetic film medium can be reduced.
It is possible to obtain a perpendicular magnetic recording medium suitable for ultra-high-density magnetic recording which is excellent in stability of recording magnetization with small medium noise.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a basic structure of a perpendicular magnetic recording medium according to the present invention.

FIG. 2 is an explanatory diagram of a perpendicular magnetic recording medium according to the first embodiment.

FIG. 3 is a comparative explanatory view of a magnetic domain structure.

FIG. 4 is a comparative explanatory diagram of noise spectra of the medium of the present invention and a comparative medium.

FIG. 5 is an explanatory diagram of a perpendicular magnetic recording medium according to a second embodiment.

FIG. 6 is a comparative explanatory view of a magnetic domain structure.

FIG. 7 is an explanatory diagram of a relationship between a soft magnetic film thickness and medium noise.

FIG. 8 is an explanatory diagram of a noise spectrum of a medium of the present invention and a noise spectrum of a comparative medium.

FIG. 9 is an explanatory diagram of a magnetic storage device.

[Explanation of symbols]

11: substrate, 12: backing magnetic layer, 13: hard magnetic film, 1
4: soft magnetic film, 14-1: polycrystalline soft magnetic film, 14-2:
Amorphous soft magnetic film, 15: structure control layer, 16: perpendicular magnetization film, 17: protective layer, 31: magnetic disk, 32: magnetic head, 33: suspension, 34: actuator,
35: voice coil motor, 36: recording / reproducing circuit, 3
7: Positioning circuit, 38: Interface control circuit.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01F 10/16 H01F 10/16 41/18 41/18 (72) Inventor Atsushi Kikukawa 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo (56) References JP-A-11-191217 (JP, A) JP-A-7-129946 (JP, A) JP-A-9-16940 (JP, A) JP-A-60-83218 ( JP, A) JP-A-61-120333 (JP, A) JP-A-4-269814 (JP, A) JP-A-4-337519 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) G11B 5/62-5/858

Claims (6)

(57) [Claims] 1. A perpendicular magnetic recording medium in which a perpendicular magnetic film is provided on a substrate via a backing magnetic layer, wherein the backing magnetic layer is formed on a side close to the substrate and has a hard magnetic film whose easy axis of magnetization is vertically oriented; And a soft magnetic film formed on the hard magnetic film. 2. The perpendicular magnetic recording medium according to claim 1, wherein the coercive force of the hard magnetic film is 1 kOe or more, and the soft magnetic film is an amorphous soft magnetic film having a coercive force of 1 Oe or less. Characteristic perpendicular magnetic recording medium. 3. The perpendicular magnetic recording medium according to claim 1, wherein the coercive force of the hard magnetic film is 1 kOe or more, and the soft magnetic film is formed by forming an amorphous soft magnetic film on a polycrystalline soft magnetic film. A perpendicular magnetic recording medium having a laminated structure and a coercive force of 1 Oe or less. 4. The perpendicular magnetic recording medium according to claim 3 , wherein the amorphous soft magnetic film is a Co—Nb—Zr-based amorphous alloy, a Co—Mo—Zr-based amorphous alloy, or a Co—W— Zr-based amorphous alloy, Co-Ta-Zr-based amorphous alloy, Co-N
The polycrystalline soft magnetic film is made of any material selected from i-Zr-based amorphous alloys, and the polycrystalline soft magnetic film is made of an Fe-Al-Si-M alloy (M: Cr, Ti), Fe-Ta-CM. Alloy (M:
Al, Cr), Fe-Hf-CM alloy (M: Al, C
r), Fe-Ta-NM alloy (M: Al, Cr), N
The hard magnetic film is made of any material selected from an i-Fe-M alloy (M: Nb, Mo), and the hard magnetic film has Co as a main component and any one of Cr, Pt, Ta, Hf, and Sm added thereto. A perpendicular magnetic recording medium characterized by being made of an alloy. 5. The perpendicular magnetic recording medium according to claim 1, further comprising a nonmagnetic structure control layer having a thickness of 1 to 10 nm between said backing magnetic layer and said perpendicular magnetization film. A perpendicular magnetic recording medium characterized by the above-mentioned. 6. A magnetic head including a magnetic recording medium, a driving unit for driving the magnetic recording medium, a recording unit and a reproducing unit, and a magnetic head for moving the magnetic head relative to the magnetic recording medium. 6. A magnetic storage device comprising: a head driving unit; and a signal processing unit for processing a recording signal and a reproduction signal of a magnetic head, wherein the perpendicular magnetic recording medium according to claim 1 is used as the magnetic recording medium. A magnetic storage device.