JP2001331918A - Magnetic recording medium, its manufacturing method and magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium excellent in magnetic characteristics such as coercive force. SOLUTION: A non-magnetic base film containing Cr is provided on a substrate and a magnetic film consisting of a Co alloy containing B is provided on the non-magnetic base film. In the vicinity of the boundary of the non- magnetic base film and the magnetic film, a region R1 where the concentration of B is >=1 at.% is specified to have <=40 at.% Cr concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used for a magnetic disk drive and the like, a method for manufacturing the same, and a magnetic recording / reproducing apparatus using the magnetic recording medium.

[0002]

2. Description of the Related Art Higher recording densities have been demanded for magnetic recording media used in magnetic disk devices and the like, and accordingly, improvements in coercive force have been demanded. As a magnetic film material capable of increasing the coercive force, a CoCrTa-based alloy, particularly Pt
A CoCrPtTa-based alloy is used. In recent years, with the demand for higher recording density, a Co alloy containing B has attracted attention as a magnetic film material capable of achieving a high coercive force. B-containing Co alloys, especially Co containing Pt
In a CrPtB-based alloy, not only can a very high coercive force be obtained, but also B has an effect of making crystal grains fine.
As a result, the magnetic crystal grains can be made smaller, so that medium noise can be reduced. JP-A-4-221418 and JP-A-5-205239 disclose magnetic recording media in which a magnetic layer made of a CoCrPtB-based alloy is formed on a Cr underlayer.

[0003]

However, in a conventional magnetic recording medium using a Co alloy containing B, it is difficult to enhance the orientation and to stably enhance magnetic properties such as coercive force. there were. The present invention has been made in view of the above circumstances, and has as its object to provide a magnetic recording medium having excellent magnetic properties such as coercive force, a method for manufacturing the same, and a magnetic recording and reproducing apparatus using the magnetic recording medium. I do.

[0004]

Means for Solving the Problems The present inventor has proposed that when a magnetic film made of a Co alloy containing B is formed on a base film containing Cr, a magnetic film in the base film near the boundary between the base film and the magnetic film is formed. It has been found that Cr and B in the magnetic film form a covalent bond, and that the generated covalent compound causes disorder in the orientation of the magnetic film. Based on this finding, the present invention has been completed. Improved coercive force, narrowed coercive force range, high SNR (Si
gnal to Noise Ratio, playback signal to output noise ratio),
To achieve a narrower PW50 (isolated wave half width),
It is preferable that the axis of easy magnetization (C axis) of the crystal in the magnetic film having the HCP structure (Hexagonal Close Packed) be oriented in the plane. In order to improve the orientation of the magnetic film, it is preferable to provide the magnetic film on a base film made of Cr or a Cr alloy. In general, when a base film made of Cr or a Cr alloy is formed on a magnetic recording medium substrate having a NiP film on the surface, the base film grows so that the (200) crystal plane mainly becomes the surface. The (200) crystal plane of this underlayer is H
Since the interstitial distance is close to the (110) crystal plane in the Co alloy having the CP structure, the magnetic film that grows epitaxially with respect to the base film grows so that the (110) crystal plane becomes the surface. The present inventors have conducted intensive studies and found that when the Co alloy constituting the magnetic film contains B, Cr in the underlayer and B in the magnetic film are covalently bonded near the boundary between the underlayer and the magnetic film. Are formed, and the generated covalent compound inhibits epitaxial growth of the magnetic film.
0) It has been found that the orientation of the magnetic film is disturbed since crystal growth such that the crystal plane becomes the surface does not occur, and as a result, magnetic properties such as coercive force may be deteriorated. Therefore, in the vicinity of the boundary between the underlayer and the magnetic film, Cr and B
By lowering the concentration of either Cr or B so that does not generate a covalent bond compound, it is possible to prevent the orientation in the magnetic film from deteriorating.

[0005] The magnetic recording medium of the present invention has a structure in which Cr is deposited on a substrate.
Is provided, and a Co containing B is provided thereon.
A magnetic film made of an alloy is provided, and a Cr concentration in a region where the B concentration is 1 at% or more is 40 at% or less in the vicinity of the boundary between the non-magnetic underlayer and the magnetic film. . In the present invention, by setting the concentrations of Cr and B in the above range, it is possible to prevent Cr and B from coexisting at a high concentration in the vicinity of the boundary,
And B minimize the formation of a covalent compound,
It is possible to prevent the orientation in the magnetic film from being reduced due to the covalent compound. Therefore, magnetic characteristics such as coercive force can be improved. The Co alloy constituting the magnetic film contains Pt, and the concentration of Pt is 1 to
It is preferably 20 at%, and the concentration of B is preferably 1 to 10 at%. Further, in the present invention, the magnetic film has a structure in which many magnetic crystal grains are separated from each other by a grain boundary layer,
The average grain size of the magnetic crystal grains is preferably 6 to 20 nm. The non-magnetic underlayer is made of Cr or a Cr alloy, and this Cr alloy is made of CrMo, CrW, CrV
It is preferable to use one or more of Cr-based and CrTi-based. The surface average roughness Ra of the non-magnetic substrate is 0.1.
The thickness is preferably 1 to 1 nm. Further, the method of manufacturing a magnetic recording medium of the present invention is a method of manufacturing a magnetic recording medium in which a nonmagnetic underlayer containing Cr is provided on a substrate, and a magnetic film made of a Co alloy containing B is provided thereon. In forming the magnetic film, the Cr concentration in the region where the B concentration is 1 at% or more is 40 at% or less in the vicinity of the boundary between the non-magnetic underlayer and the magnetic film. Further, the magnetic recording and reproducing apparatus of the present invention includes a magnetic recording medium, and a magnetic head for recording and reproducing information on and from the magnetic recording medium, wherein the magnetic recording medium is provided with a nonmagnetic underlayer containing Cr on a substrate, A magnetic film made of a Co alloy containing B is provided thereon, and near the boundary between the nonmagnetic underlayer film and the magnetic film, the C film in the region where the B concentration is 1 at% or more is provided.
The r concentration is set to 40 at% or less.

[0006]

FIG. 1 shows an embodiment of a magnetic recording medium according to the present invention. The magnetic recording medium shown in FIG.
A non-magnetic substrate 1, a magnetic film 3, a protective film 4, and a lubricating layer 5 are sequentially formed on a non-magnetic substrate 1.

As the non-magnetic substrate 1, an aluminum substrate, a glass substrate, a ceramic substrate, a carbon substrate, a flexible resin substrate, a substrate obtained by forming a NiP film on these substrates by plating or sputtering, or the like can be used. .
Also, a NiAl film can be formed on the surface of the substrate 1 instead of the NiP film. In the case where a NiAl film is used, a thickness of 10 to 100 nm is preferable because the orientation of the base film 2 can be improved.

The surface of the nonmagnetic substrate 1 is preferably textured in the circumferential direction so that the surface has an average surface roughness R
a is 0.1 to 1 nm (1 to 10 °), preferably 0.2
It is desirable to set it to 0.8 nm (2-8 °). When the surface average roughness Ra is less than the above range, the non-magnetic substrate 1 becomes excessively smooth, and the orientation of the base film 2 and the magnetic film 3 in the circumferential direction decreases. If the surface average roughness Ra exceeds the above range, the crystal grains in the non-magnetic underlayer 2 become large, the magnetic crystal grains in the magnetic film 3 become coarse, and the medium noise increases. When the non-magnetic substrate 1 is used without texture processing, the surface average roughness Ra is set to 0.5 nm or less (5
Å, preferably 0.2 nm or less (2 Å or less).

The non-magnetic underlayer 2 is used to improve the orientation of the magnetic film 3 and is preferably made of Cr or a Cr alloy. The Cr alloy includes CrMo-based, CrW-based, CrV-based, and CrTi-based.
One or more of the systems can be used. C
When an rMo-based, CrW-based, CrV-based, or CrTi-based alloy is used, the concentration of Mo, W, V, and Ti is 0.1 to 30.
at%. In addition, the non-magnetic base film 2 includes
A material obtained by adding another element to the above-described material as long as the crystallinity of the base film 2 is not impaired can be used.

The nonmagnetic underlayer 2 may have a single-layer structure or a multilayer structure in which a plurality of films made of the same or different materials are laminated. For example, Cr composed of Cr
It can be a multilayer film in which a plurality of layers and a Cr alloy layer made of the above-mentioned Cr alloy are laminated. It is desirable that the thickness of the nonmagnetic underlayer 2 be 1 to 100 nm (10 to 1000 °), preferably 2 to 50 nm (20 to 500 °). If the thickness is less than the above range, the orientation decreases, and if the thickness exceeds the above range, the crystal grains become large and the magnetic crystal grains in the magnetic film 3 become coarse.

The magnetic film 3 is made of a Co alloy containing B. As this Co alloy, a CoCrB-based alloy can be used, and particularly, a CoCrPtB-based alloy containing Pt is preferably used. The concentration of B in the Co alloy is preferably 1 to 10 at% (preferably 2 to 7 at%, more preferably 2.5 to 6 at%). B
If the concentration is less than the above range, the coercive force is reduced, and the magnetic crystal grains are enlarged to increase the noise. If the concentration exceeds the above range, the orientation in the magnetic film 3 may be reduced and the coercive force may be reduced. The Cr concentration in the Co alloy is 40 at% or less (preferably 5 to 35 at
%, More preferably 10 to 25 at%).

In the case of using a CoCrPtB-based alloy containing Pt, if the concentration of Pt in the alloy is too low, the effect of increasing the coercive force is reduced. If the Pt concentration is too high, the magnetization of the magnetic film 3 becomes small and the coercive force becomes high. However, in order to obtain a sufficient reproduction signal output, it is necessary to make the magnetic film 3 thick. This leads to an increase in noise. Therefore, the concentration of Pt is 1 to 20a.
t% (preferably 3 to 16 at%, more preferably 6 at%
１４14 at%). The Co alloy includes one or more of Ta, Zr, Cu, and Nb.
More than one species may be included. The magnetic film 3 may have a single-layer structure or a multilayer structure in which a plurality of films made of the same or different materials are stacked.

The thickness of the magnetic film 3 is 5 to 100 nm (50
Å1000 °). If the thickness of the magnetic film 3 is less than the above range, the coercive force decreases. The magnetic film 3
If the thickness exceeds the above range, the magnetic crystal grains in the magnetic film 3 are likely to be coarsened, and the noise characteristics may be reduced. The thickness of the magnetic film 3 is 10 to 50 nm (100 to 5 nm).
00 °) is more preferable. If the thickness is less than this range, the output of the reproduction signal decreases, and if it exceeds the above range, the output of the reproduction signal decreases in recording and reproduction in a high frequency region desired for recording at a high recording density.

FIG. 2 shows the distribution of the chemical composition in the thickness direction near the boundary between the non-magnetic underlayer 2 and the magnetic film 3 in the magnetic recording medium of this embodiment. As shown in this figure, in the vicinity of the boundary between the nonmagnetic underlayer 2 and the magnetic film 3, the Cr concentration gradually decreases from the substrate side to the surface side, and the B concentration gradually increases.

As shown in FIG. 1, in the magnetic recording medium of the present embodiment, the B concentration is 1 at% near this boundary.
The Cr concentration in the above region R1 is set to be 40 at% or less. If the Cr concentration in this region R1 exceeds 40 at%, the orientation of the magnetic film 3 deteriorates, and the coercive force decreases. The chemical composition distribution shown here indicates the average distribution in the in-plane direction of the substrate.

Hereinafter, the concentration distributions of Cr and B near the boundary between the non-magnetic underlayer 2 and the magnetic layer 3 will be described in detail. FIG. 3A shows the fine structure of the magnetic film 3. As shown in FIG. 3A, the magnetic film 3 has a large number of magnetic crystal grains 3 made of a Co alloy (for example, a CoCrPtB-based alloy).
a have a structure separated from each other by the grain boundary layer 3b. The average grain size of the magnetic crystal grains 3a in the in-plane direction of the substrate is 6 to
Preferably, it is 20 nm (60-200 °). The average grain size of the magnetic crystal grains 3a is desirably 7 to 15 nm (preferably 8 to 10 nm). If the particle size is less than the above range, the influence of thermal demagnetization increases, and if the particle size exceeds the above range, medium noise increases, which is not preferable. The particle size of the magnetic crystal grains 3a can be measured based on, for example, an image obtained by a TEM (transmission electron microscope). The grain boundary layer 3b is composed of the same components as the magnetic crystal grains 3a (for example, a CoCrPtB-based alloy), but the composition is different from the composition of the magnetic crystal grains 3a, and the concentrations of Cr and B are different from those in the magnetic crystal grains 3a. It becomes higher than the concentrations of Cr and B. Reference numeral 3c denotes a segregation layer in which the concentration of B is higher than that of the magnetic crystal grains 3a, similarly to the grain boundary layer 3b.

FIG. 3B shows the distribution of the chemical composition in the film thickness direction near the boundary between the nonmagnetic underlayer 2 and the magnetic film 3 in the magnetic crystal grain 3a (that is, at the position indicated by the symbol A). It is. The magnetic film 3 near the boundary with the non-magnetic underlayer 2 (that is, the lowermost layer portion) is a Cr-concentration reduced region 6 where the Cr concentration gradually decreases from the non-magnetic underlayer 2 toward the magnetic film 3. The component concentration continuously changes in the Cr concentration reduced region 6 because the material of the magnetic film 3 attached to the surface of the base film 2 is mixed with the material of the base film 2 by diffusion in the initial stage of the growth of the magnetic film 3. it is conceivable that. On the uppermost layer side of the Cr concentration reduced region 6, the Cr concentration is sufficiently low, that is, 40 at% or less.
The segregation layer 3c in which the concentration of B is higher than that of the magnetic crystal grains 3a is formed in the magnetic film 3 immediately above the Cr concentration-reduced region 6 as in the grain boundary layer 3b.
, The concentration of Cr is sufficiently low, that is, 40a
t% or less. For this reason, it becomes difficult for Cr and B to generate a covalently bonded compound.

When a non-magnetic substrate 1 having a NiP film on its surface is used, the non-magnetic base film 2 is mainly composed of (2
00) Growing such that the crystal plane becomes the surface. Since the (200) crystal plane of the underlayer 2 is closer to the (110) crystal plane of the Co alloy having the HCP structure, the magnetic film 3 that grows epitaxially with respect to the underlayer 2 is (11).
0) Growing such that the crystal plane becomes the surface. When a non-magnetic substrate 1 having a NiAl film on the surface is used, the non-magnetic underlayer 2 is grown so that the (112) crystal plane mainly becomes the surface. The (112) crystal plane of the underlayer 2 is closer to the (100) crystal plane of the Co alloy having the HCP structure, so that the magnetic film 3 which grows epitaxially with respect to the underlayer 2 has the (100) crystal plane. Grows to become the surface.

The protective film 4 is for preventing corrosion of the magnetic film 3 and for preventing damage to the medium surface. Conventionally known materials can be used, for example, C, SiO ₂ , ZrO ₂ , or those containing these as main components. Those containing other elements can be used. Protective film 4
Is preferably 1 to 20 nm (that is, 10 to 200 °) from the viewpoint of corrosion resistance and slidability. Furthermore, in order to reduce the spacing loss and obtain a sufficient reproduction output,
The thickness is preferably 10 nm (10 to 100 °).

The lubricating layer 5 is made of perfluoropolyether,
It is preferably formed using a fluorinated alcohol, a fluorinated carboxylic acid, or the like.

Next, a method of manufacturing the magnetic recording medium according to the present embodiment will be described with reference to an example of manufacturing the magnetic recording medium having the above-described configuration. When a non-magnetic substrate 1 having a NiP film formed on its surface is used, the temperature at the time of forming the base film is preferably 180 to 250 ° C. from the viewpoint of improving the orientation of the base film 2. A non-magnetic base film 2 is formed on a non-magnetic substrate 1 by sputtering using Cr or a Cr alloy.

In the manufacturing method of the present embodiment, when forming the magnetic film 3 on the nonmagnetic underlayer 2, in the region R1 where the B concentration near the boundary between the nonmagnetic underlayer 2 and the magnetic film 3 is 1 at% or more. The film is formed so that the Cr concentration is 40 at% or less.

In the region R1 having a B concentration of 1 at% or more, for example, the following method can be used to form a film so that the Cr concentration is 40 at% or less. In this method, of the constituents of the magnetic film 3, the first target made of a material having a B concentration of less than 1 at% and the Cr concentration of 40 at% or less, and the second target made of the constituent material of the magnetic film 3.
Prepare a target. Examples of the materials of the first and second targets include the following. The magnetic film 3 is made of Co-22at% Cr-10at% P
In the case where the first target is made of t-5 at% B (Co22Cr10Pt5B), CoC is used as the material of the first target.
r alloy, for example, Co-40 at% Cr (Co40Cr)
And Co22Cr10Pt5B which is a constituent material of the magnetic film 3 can be used as a material of the second target.

First, a material for the first target is deposited on the non-magnetic underlayer 2 by a sputtering method using a first target having a Cr concentration of 40 at% or less. In the process of adhering the first target constituent material onto the non-magnetic base film 2, this material is mixed with the base film material having a high Cr concentration at the very beginning, and although the Cr concentration increases, the Cr increases as the material grows. The concentration decreases and finally 40
at% or less. As shown in FIG. 2, the Cr concentration on the uppermost layer side (outermost surface side) of the region R2 formed by the first target is 40 at% or less. This region R2 corresponds to the Cr concentration reduced region 6 in FIG.
Is equivalent to

Next, a second target material is adhered thereon using a second target made of the constituent material of the magnetic film 3. Thus, the magnetic film 3 is formed. In the first and second target constituent materials adhered on the non-magnetic base film 2, a part of the components is segregated, and FIG.
As shown in (1), the magnetic film 3 has a structure in which many magnetic crystal grains 3a are separated from each other by a grain boundary layer 3b.

In the region formed by the second target made of the constituent material of the magnetic film 3, the B concentration is 1 at% or more. On the uppermost layer side of the region R2 formed by the first target, the Cr concentration is 40 at% or less. Therefore, in the obtained magnetic recording medium, the Cr concentration in the region R1 where the B concentration is 1 at% or more near the boundary between the nonmagnetic underlayer 2 and the magnetic film 3 is 40 at% or less.

FIG. 4 shows an example of a magnetic recording and reproducing apparatus using the above magnetic recording medium. The magnetic recording / reproducing apparatus shown here includes a magnetic recording medium 7 having a configuration shown in FIG. 1, a medium driving unit 8 for driving the magnetic recording medium 7 to rotate, a magnetic head 9 for recording / reproducing information on / from the magnetic recording medium 7, A head drive unit 10 and a recording / reproducing signal processing system 11 are provided.
The recording / reproducing signal processing system 11 can process a recording signal from the outside and send it to the magnetic head 9, or process a reproduction signal from the magnetic head 9 and send it to the outside.

In the magnetic recording medium of the present embodiment, the B concentration is 1a near the boundary between the non-magnetic underlayer 2 and the magnetic layer 3.
Since the Cr concentration in the region R1 of t% or more is set to be 40 at% or less, it is possible to prevent the orientation of the magnetic film 3 from being disturbed and to enhance the magnetic characteristics such as the coercive force. The reason that the orientation of the magnetic film 3 can be prevented from being disordered can be considered as follows.

When the Co alloy constituting the magnetic film contains B, Cr in the underlayer and B in the magnetic film form a covalent bond near the boundary between the underlayer and the magnetic film, and the generated covalent bond In some cases, the epitaxial growth of the magnetic film is hindered by the conductive compound, the orientation in the magnetic film is disturbed, and magnetic properties such as coercive force may be degraded. In the magnetic recording medium of the present embodiment, the C value near the boundary between the non-magnetic under film 2 and the magnetic film 3
By setting the concentrations of r and B in the above range, it is possible to prevent Cr and B from coexisting at a high concentration near the boundary. Therefore, generation of a covalent compound between Cr and B can be suppressed as much as possible, and a decrease in the orientation in the magnetic film 3 due to the covalent compound can be prevented.

On the other hand, as can be seen from the average distribution of the chemical composition shown in FIG. 5, near the boundary between the non-magnetic underlayer 2 and the magnetic film 3, the Cr concentration in the region R3 having a B concentration of 1 at% or more is 40 at. %, The Cr concentration and B
In the high concentration region R3, Cr and B form a covalent compound, and the covalent compound disturbs the orientation in the magnetic film. As a result, magnetic properties such as coercive force deteriorate. Such a chemical composition distribution indicates that the second target made of the constituent material of the magnetic film 3 is formed on the nonmagnetic base film 2 without using the first target when forming the magnetic film 3 on the nonmagnetic base film 2. It is obtained when a film is formed directly by using. This is because in the process of forming the magnetic film 3,
This is because the B concentration exceeds 1 at% before the Cr concentration decreases to 40 at% or less. FIG. 6A and FIG.
(B) shows the fine structure in the case where the magnetic film 3 is directly formed on the non-magnetic underlayer 2, and the distribution of the chemical composition in the thickness direction of the magnetic crystal grains 3a (that is, at the position indicated by the symbol A '). Things. As shown in FIG. 6B, in this magnetic recording medium, the non-magnetic base film 2 and the magnetic film 3
In the vicinity of the boundary with, the Cr concentration gradually decreases from the nonmagnetic underlayer 2 toward the magnetic film 3, but the segregation layer 3 c is formed in the lowermost layer of the magnetic film in contact with the nonmagnetic underlayer 2. Therefore, in the segregation layer 3c, the Cr concentration increases. As described above, in the segregation layer 3c having a high B concentration, C
Since the r concentration is high, Cr and B easily form a compound having a covalent bond.

Further, according to the method for manufacturing a magnetic recording medium of the present invention, it is possible to manufacture a magnetic recording medium capable of preventing the orientation of the magnetic film 3 from being disturbed and increasing the coercive force. Further, according to the magnetic recording / reproducing apparatus of the present invention, it is possible to increase the coercive force of the magnetic recording medium and increase the recording density.

In the manufacturing method according to the above embodiment, prior to using the second target made of the constituent material of the magnetic film 3, the B concentration of the constituent components of the magnetic film 3 is less than 1 at% and the Cr concentration is 40 at% or less. A first made of a material that is
Although the method using a target has been exemplified, in the present invention, the first target is not limited to the one composed of the constituent components of the magnetic film 3, and even if the first target is diffused into the magnetic film 3 formed by the second target, the orientation is reduced. Any material may be used as long as it does not cause magnetic deterioration. As a material of the first target, for example, a NiCr alloy can be used. NiCr alloy has a crystal structure of H
Although it has a crystal structure different from the CP structure, Ni
Can be used as the first target material because there is no risk of deteriorating the magnetic properties even when it is dissolved in a Co alloy that forms

Further, in the manufacturing method of the above embodiment, the method using the first and second targets is exemplified, but in the present invention, the number of targets to be used may be three or more. For example, Co having a Cr concentration of 40 at% or less is used.
Using a first target made of a Cr alloy, a second target made of a CoPt alloy, a third target made of a CoB alloy, and a fourth target made of Cr, B was not included in the initial stage of film formation (B concentration was low). A target material is deposited on the non-magnetic underlayer 2 using the first and second targets having a Cr concentration of 40 at% or less and the first and second targets having a Cr concentration of 40 at% or less. A method of forming a film using a third target including B and a fourth target in addition to the second target and the second target can be employed.

In the present invention, when a Co alloy containing Ta is used for the magnetic film 3, the total of the B concentration and the Ta concentration is 1 a near the boundary between the nonmagnetic base film 2 and the magnetic film 3.
It is preferable that the Cr concentration in the region of t% or more be 40 at% or less. This is because Ta, like B, can form a covalent bond with Cr, so that the Cr concentration is 4% in the region where the total of the B concentration and the Ta concentration is 1 at% or more.
If the content exceeds 0 at%, Ta and / or B may form a covalent bond with Cr, and the generated covalent compound may cause disorder in the orientation of the magnetic film.

[0035]

EXAMPLES Hereinafter, the working effects of the present invention will be clarified by showing specific examples. The magnetic recording medium shown in FIG. 1 was manufactured as follows. (Examples 1 to 8) After polishing an aluminum substrate 1 (diameter 95 mm, thickness 0.8 mm) having a NiP film (thickness 10 μm) formed on the surface thereof by electroless plating, texturing was performed to obtain a surface average roughness. Ra was set to 0.5 nm. Next, on the non-magnetic substrate 1, using a DC magnetron sputtering apparatus (3010 manufactured by Anelva), the non-magnetic base film 2,
The magnetic film 3 was formed by a sputtering method. When forming the magnetic film 3, at the initial stage of film formation, Co-4 containing no B is used.
0 at% Cr (Co40Cr) or Ni-40 at%
Using a first target made of Cr (Ni40Cr),
Next, Co-22 at% Cr-10 at% Pt-5 at
The film was formed using a second target made of% B (Co22Cr10Pt5B). In Examples 1 to 3 and 5 to 7, the nonmagnetic underlayer 2 was a two-layer structure film including a first underlayer made of Cr and a second underlayer made of a Cr alloy. Prior to film formation, the degree of vacuum in the chamber of the sputtering apparatus was 9 ×
It was set to 10 ⁻⁶ Pa. The chamber pressure during film formation was 6 × 1
0 ^-1 Pa. A protective film 4 (thickness: 80 °) made of carbon is formed on the magnetic film 3 by sputtering, and a lubricating film 5 (Z-Dol, Fomblin) (thickness: 1) is formed thereon.
7)) was formed by a dipping method, and tape burnishing was performed. The obtained magnetic recording medium was confirmed to be able to achieve a glide height of 0.7 μinch using a BG tester.

(Comparative Examples 1 to 4) When forming the magnetic film 3, the magnetic film was formed in the same manner as in the embodiment except that the film was formed using only the second target made of Co22Cr10Pt5B without using the first target. A recording medium was produced.

FIGS. 7 to 9 show the chemical compositions in the film thickness direction of the magnetic recording media of Examples 4, 8 and Comparative Example 4 obtained by using an Auger spectrometer (MicroLab-310F manufactured by VG Scientific). FIG. The measurement conditions at the time of measurement by Auger spectroscopy are as follows.
Acceleration voltage: 10 kV, ion source: Ar, sample voltage: 45
nA.

The electromagnetic conversion characteristics of these magnetic recording media are represented by G
UZIK read / write analyzer RWA1632,
And it measured using the spin stand S1701MP. To evaluate the electromagnetic conversion characteristics, a composite thin film magnetic recording head having a giant magnetoresistive (GMR) element in the reproducing section was used as the magnetic head, and the recording conditions were set to a linear recording density of 280 kF.
The measurement was performed as CI. Tables 1 and 2 show the measurement results of the magnetostatic characteristics and the electromagnetic conversion characteristics of the magnetic recording media of the above Examples and Comparative Examples. In the table, Hc indicates a coercive force. S *
Creates a B-H hysteresis loop using a vibrating magnetic property measuring device (VSM). In this hysteresis loop, the value of H at B = 0 is set to Hc and -Hc. The intersection of the tangent and the straight line B = -Br is determined, and the value of H at this point is expressed as H *.
, And is a value obtained by using the following equation. S *
= (H *) / Hc If this S * is small, even though the saturation magnetization of the magnetic recording medium is large, the residual magnetization which is a substantially important characteristic is small, so that the electromagnetic conversion characteristics necessary for recording and reproduction can be obtained. Disappears. Therefore, S * can be used as an index of high Br. Generally, a Co alloy film having S * of 0.8 or more is:
It can be said that it is preferable as a magnetic film. When S * of the magnetic recording medium is small, it can be considered that the coercive force of the magnetic domain, which is a unit of magnetization in the magnetic film, greatly varies among the magnetic domains. It is considered that this is because the crystal orientation of the Co alloy forming the magnetic film deteriorates. In such a state, even if the average coercive force of the entire magnetic film is increased, many magnetic domains having a small coercive force are included.
These magnetic domains are more susceptible to a demagnetizing field at the time of writing, and the recording thereof undergoes reversal degaussing, that is, the residual time, which is a substantially important characteristic, is reduced. As a result, the output at the time of reading decreases. From the above, it can be estimated that the demagnetizing field becomes stronger at a higher recording density in a magnetic recording medium having a small S *. LF indicates a reproduced signal output during low-frequency (20 MHz) recording. OW indicates the residual amount of the low frequency signal when the high frequency (160 MHz) recording is superimposed on the low frequency (20 MHz) recording. PW50 indicates a solitary wave half width. SNR
Indicates a reproduction signal to output noise ratio. The Cr concentration when B is 1 at% indicates the Cr concentration when the B concentration is 1 at% in the vicinity of the boundary between the non-magnetic underlayer 2 and the magnetic film 3.

[0039]

[Table 1]

[0040]

[Table 2]

From Tables 1 and 2, at the initial stage of the formation of the magnetic film 3, Co40Cr or Ni
A first target of 40Cr was used, followed by Co22
By forming a film using the second target made of Cr10Pt5B, the Cr content when the B concentration is 1 at% is obtained.
The magnetic recording medium of the embodiment in which the concentration is 40 at% or less,
Film formation is performed using only the second target, and the B concentration is 1a.
It can be seen that the magnetic properties such as the coercive force are superior to the magnetic recording medium of the comparative example in which the Cr concentration at t% exceeds 40 at%.

[0042]

As described above, in the magnetic recording medium of the present invention, the vicinity of the boundary between the non-magnetic underlayer and the magnetic film is improved.
The Cr concentration in the region where the B concentration is 1 at% or more is 40a.
t% or less, it is possible to prevent Cr and B from coexisting at a high concentration near the above boundary,
And B minimize the formation of a covalent compound,
It is possible to prevent the orientation in the magnetic film from being reduced due to the covalent compound. Therefore, magnetic characteristics such as coercive force can be improved. Further, according to the method for manufacturing a magnetic recording medium of the present invention, it is possible to manufacture a magnetic recording medium capable of preventing the orientation of the magnetic film from being disturbed and increasing the coercive force. According to the magnetic recording / reproducing apparatus of the present invention,
It is possible to increase the coercive force of the magnetic recording medium and increase the recording density.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing one embodiment of a magnetic recording medium of the present invention.

FIG. 2 is a schematic diagram showing an average distribution of a chemical composition in a film thickness direction near a boundary between a nonmagnetic base film and a magnetic film in the magnetic recording medium shown in FIG.

3A is a schematic diagram showing a fine structure of the magnetic recording medium shown in FIG. 1, and FIG. 3B is a schematic diagram showing a distribution of a chemical composition of a magnetic crystal grain in a film thickness direction.

FIG. 4 is a schematic configuration diagram showing an example of a magnetic recording / reproducing apparatus using the magnetic recording medium shown in FIG.

FIG. 5 is a schematic diagram showing an average distribution of a chemical composition in a film thickness direction near a boundary between a nonmagnetic underlayer and a magnetic film in a magnetic recording medium in which a constituent material of a magnetic film is directly formed on a nonmagnetic underlayer. .

FIG. 6A is a schematic diagram showing a fine structure of a magnetic recording medium in which a constituent material of a magnetic film is directly formed on a non-magnetic base film;
(B) Schematic diagram showing the distribution of the chemical composition in the thickness direction of the magnetic crystal grains.

FIG. 7 is a schematic diagram showing an average distribution of a chemical composition in a film thickness direction near a boundary between a nonmagnetic underlayer film and a magnetic film of a magnetic recording medium of an example.

FIG. 8 is a schematic diagram illustrating an average distribution of a chemical composition in a film thickness direction near a boundary between a nonmagnetic underlayer film and a magnetic film of the magnetic recording medium of the example.

FIG. 9 is a schematic diagram illustrating an average distribution of a chemical composition in a film thickness direction near a boundary between a nonmagnetic underlayer film and a magnetic film of a magnetic recording medium of a comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Non-magnetic base film, 3 ... Magnetic film, 3a ...
Magnetic crystal grains, 3b ... grain boundary layer, 7 ... magnetic recording medium, 9 ...
・ Magnetic head

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D006 BB01 BB06 BB07 CA01 DA03 FA09 5D112 AA03 AA05 AA24 BB05 BB06 BD04 FA04

Claims (7)

[Claims] A non-magnetic base film containing Cr is provided on a substrate, and a magnetic film made of a Co alloy containing B is provided thereon. Near the boundary between
A magnetic recording medium characterized in that a Cr concentration in a region (R1) having a concentration of 1 at% or more is 40 at% or less. 2. The magnetic film according to claim 1, wherein the Co alloy contains Pt, the Pt concentration is 1 to 20 at%, and B
2. The magnetic recording medium according to claim 1, wherein the concentration of the magnetic recording medium is 1 to 10 at%. 3. The magnetic film has a structure in which a number of magnetic crystal grains (3a) are separated from each other by a grain boundary layer (3b).
3. The magnetic recording medium according to claim 1, wherein the average diameter of the magnetic crystal grains is 6 to 20 nm. 4. The non-magnetic underlayer is made of Cr or a Cr alloy, and this Cr alloy is made of CrMo, CrW, C
The magnetic recording medium according to any one of claims 1 to 3, wherein the magnetic recording medium is at least one of rV-based and CrTi-based. 5. A non-magnetic substrate having a surface average roughness Ra of 0.5.
The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a thickness of 1 to 1 nm. 6. A method for manufacturing a magnetic recording medium comprising: providing a nonmagnetic underlayer containing Cr on a substrate, and providing a magnetic film made of a Co alloy containing B on the substrate. A method for manufacturing a magnetic recording medium, characterized in that the Cr concentration in a region where the B concentration is 1 at% or more is 40 at% or less near the boundary between the non-magnetic underlayer and the magnetic film. 7. A magnetic recording medium comprising: a magnetic recording medium; a magnetic head for recording / reproducing information on / from the magnetic recording medium; and a magnetic recording medium provided with a non-magnetic underlayer containing Cr on a substrate. A magnetic film made of a Co alloy containing B is provided thereon, and a Cr concentration in a region where the B concentration is 1 at% or more near the boundary between the nonmagnetic underlayer film and the magnetic film is 4%.
A magnetic recording / reproducing apparatus, wherein the magnetic recording / reproducing apparatus is set to 0 at% or less.