JPH10241935A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which does not produce much noise, has high resolution, an average particle diameter which is controlled to reduce particle size fluctuation, an appropriate Hc (coercive force), and an improved S* (coercive force squareness ratio). SOLUTION: A magnetic recording medium has a base layer 21 and a magnetic thin film 22 in which magnetic particles 22b are scattered in a nonmagnetic base material 22a on a substrate 11. In a method for manufacturing the medium, the magnetic particles 22b are deposited on the base layer 21 in a state where the main component of the nonmagnetic base material 22a is preferentially deposited on the base layer 21 material by supplying the main component of the base layer 21 and the raw material of the magnetic particles 22b and accelerating the surface movement of the material to be deposited on the base layer 21 after the base layer 21 is formed. Therefore, a magnetic recording medium having the magnetic thin film 22 formed by selectively depositing the nonmagnetic base material 22a on the base layer 21 containing the nonmagnetic base material as a main component and depositing the magnetic particles 22b and the nonmagnetic base material 22a on the selectively deposited nonmagnetic base material 22a is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium mounted on a magnetic disk drive and a method for manufacturing the same.

[0002]

2. Description of the Related Art A magnetic disk device represented by a hard disk drive (HDD) is a peripheral storage device having both large capacity, high-speed access, and high-speed data transfer. It is widely used in personal information systems such as personal computers. Further, due to an increase in the amount of data centered on moving images, there is a great demand for increasing the storage capacity of HDDs. In order to increase the storage capacity of the HDD, it is necessary to improve the areal recording density of the medium. On the other hand, since the recording bit becomes very small as the density increases, reproduction is performed using a high-sensitivity magnetoresistive read head. However, when a high-sensitivity reproducing head is used, the influence of medium noise becomes remarkable. Therefore, it is important to reduce the medium noise in the future development of magnetic recording.

In order to realize high density and low noise, it is necessary to sufficiently separate the exchange interaction between magnetic particles in a magnetic thin film. Decreasing the intergranular interaction increases the Hc of the entire magnetic thin film, enables formation of a steep magnetization transition capable of obtaining high resolution, and improves the shape of the magnetization transition portion, thereby reducing medium noise.

In order to separate the exchange interaction between magnetic particles, it is effective to physically separate the magnetic particles by interposing a non-magnetic material between the magnetic particles. For example, in a metal sputtering medium, a Co—Cr-based alloy target is Ar
Sputtering is performed in a gas to precipitate Cr between Co crystal particles. In order to control the amount of Cr precipitated, Cr grown in a cone shape is used as an underlayer, or the substrate is heated during the formation of a magnetic film to promote phase separation. However, in a metal sputtering medium having such a fine structure, the separation of the intergranular interaction is insufficient, and an aggregate (magnetic cluster) of several tens to several hundreds of magnetic particles is regarded as a minimum unit of magnetization reversal. Has become. This raises the medium noise of the metal sputtering medium and causes a reduction in resolution.

In recent years, a medium having a granular structure has attracted attention as a magnetic recording medium capable of reducing the interaction between grains and realizing a thin film and high output characteristics. The granular medium is a composite material of magnetic particles and a non-magnetic material, and has a fine structure in which magnetic particles of a predetermined size are isolated and dispersed in a non-magnetic material. In the granular medium, the magnetic particles can be effectively separated by the network structure of the non-magnetic material, so that the unit of magnetization reversal can be made one physical magnetic particle. In particular, when a non-conductive material is used as the non-magnetic material, intergranular exchange interaction via conduction electrons can be suppressed, so that even if the volume ratio of the magnetic material is set to be as high as about 50%, low noise and high output can be obtained. Easy to balance. Moreover, the granular medium can be produced by a sputtering method with high mass productivity, like the metal sputtering medium. Specifically, a method of simultaneously sputtering a magnetic target and a nonmagnetic target in Ar gas, a method of sputtering a composite target including a magnetic substance and a nonmagnetic substance, and the like can be used.

[0006] In such a granular medium,
It is important to optimize the average particle size and reduce the variation in the particle size. The average particle size is preferably small enough to cope with high linear density and large enough to withstand thermal disturbance. In addition, the variation in particle size is determined by the coercive force squareness ratio (S
^* ) Is decreased, and the magnetic field required for saturation recording is increased, which is not preferable. However, in the conventional granular medium, the examination of the underlayer, the base material, and the film forming process was insufficient, so that it was difficult to optimize the average particle size and reduce the variation in the particle size.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium having low noise, high resolution, controlled average particle diameter, small particle diameter variation, optimized Hc, and improved S ^*. To provide. Another object of the present invention is to provide a method for manufacturing such a magnetic recording medium with good controllability.

[0008]

According to the present invention, there is provided a magnetic recording medium comprising: a base layer on a base material; and a magnetic thin film in which magnetic particles are dispersed in a non-magnetic base material. And the main component of the non-magnetic base material is the same material,
It has a structure in which a nonmagnetic matrix is selectively deposited on an underlayer, and magnetic particles and a nonmagnetic matrix are deposited thereon.

The method of manufacturing a magnetic recording medium according to the present invention provides a method of manufacturing a magnetic recording medium having a base layer on a base material and a magnetic thin film in which magnetic particles are dispersed in a non-magnetic base material. After the formation, the main component of the underlayer and the raw material of the magnetic particles are supplied, the surface movement of the substance deposited on the underlayer is promoted, and the main component of the nonmagnetic base material is preferentially coated on the underlayer. It is characterized in that magnetic particles are deposited in the state of being attached.

[0010] Another method for manufacturing a magnetic recording medium of the present invention is as follows.
When manufacturing a magnetic recording medium having a magnetic thin film in which magnetic particles are dispersed in a non-magnetic base material on a base material, it is necessary to apply a substrate bias during the formation of the magnetic thin film and reduce the substrate bias during the film formation. It is a feature.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The magnetic thin film constituting the magnetic recording medium of the present invention has a fine structure in which magnetic particles are isolated and dispersed in a non-magnetic base material. In other words, it means a structure in which magnetic particles are formed in a network of non-magnetic material, inter-granular exchange interaction is substantially cut off, and the magnetization reversal unit substantially matches the physical particle size.

In one method of the present invention, after forming an underlayer on a substrate, the main component of the underlayer and the raw material of the magnetic particles are supplied, and the surface movement of a substance to be deposited on the underlayer is promoted. Then, the magnetic particles are deposited while the main component of the nonmagnetic base material is preferentially deposited on the underlayer. Therefore,
In the magnetic thin film formed by this method, the main components of the underlayer and the nonmagnetic matrix are the same, and the nonmagnetic matrix is selectively deposited on the underlayer, and the magnetic particles and the nonmagnetic matrix are deposited thereon. It has a structure in which a magnetic base material is precipitated.

This method is based on the following principle. In the present invention, the main components of the underlayer and the non-magnetic base material are made of the same material, and the surface movement of the sputtered substance, that is, the magnetic particles and the non-magnetic base material flying on the underlayer is promoted. As a means for promoting the surface movement of the sputtered substance, for example, a method is used in which a bias voltage is applied to the substrate to generate plasma near the substrate, and ions in the plasma are accelerated and incident on the growth film surface. In addition to this method, ion irradiation from an ion source, heating of the substrate surface using an infrared lamp, or the like, or a combination of these methods may be used.

When the surface movement of the sputtered material is promoted as described above, a liquid state formed by the sputtered material exists at the interface between the solid phase and the gas phase. At the start of the formation of the magnetic thin film, the ratio of the magnetic particle component and the non-magnetic base material component in the liquid phase is almost equal to that in the gas phase. This ratio is determined by the target composition and the conditions for impacting the target. In the initial process of forming the magnetic thin film, of the magnetic particles and the non-magnetic base material that have flown onto the base layer, a base material having excellent wettability with the base layer starts to precipitate preferentially on the base layer.
When the base material component starts to precipitate preferentially, the ratio of the magnetic particle component in the liquid phase gradually increases. When the magnetic particle component exceeds the critical point, the magnetic particles precipitate on the base material in a predetermined size,
At the same time, the base material precipitates in the gaps between the magnetic particles. Here, the magnetic particle having a predetermined size means a size small enough to cope with a high linear density and large enough to withstand thermal disturbance. Note that the specific particle size range depends on the design of the linear density and the magnetic anisotropy energy of the magnetic material used.

In this method, glass, aluminum, silicon, plastic or the like is used as the substrate. The shape of the substrate may be any of a disk, a tape, and a drum. CoPt, CoPt
Cr, CoTaCr, CoNiCr, CoPtCr, C
oNiTa and the like. The material of the underlayer and the nonmagnetic base material may be SiO ₂ , SiO, Si ₃ N
₄ , Al ₂ O ₃ , AlN, Ta ₂ O ₅ , TiN, BN,
Examples include CaF, TiF, C, and PTFE (polytetrafluoroethylene). It is most preferable that the combination of the base and the base material match the material and the sputtering conditions, but different sputtering conditions may be used as long as good wettability can be maintained. Further, different materials may be used for the base and the base material. When the substrate material and the base material are the same, it is not necessary to provide the underlayer. In this case, it is preferable to adjust the sputtering conditions for the granular magnetic thin film to form a base material having properties close to those of the substrate. The material of the protective film is not particularly limited, and the same material as the base material or a different material may be used.

In another method of the present invention, a substrate bias is applied at the time of forming a magnetic thin film, and the substrate bias is reduced during the film formation. In this method, a large substrate bias is applied at an early stage of forming a magnetic thin film in order to promote nucleation of magnetic particles and facilitate aggregation. On the other hand, after the nucleation, the magnetic particles aggregate even without applying the same power as at the time of the nucleation. Conversely, if a large substrate bias is always applied, the reverse sputtering effect increases,
It is effective to reduce the power of the substrate bias. The magnitude of the substrate bias depends on the presence or absence of the underlayer, magnetic particles,
It changes depending on conditions such as the sputter rate of the non-magnetic base material,
By adjusting these, the particle size and dispersibility of the magnetic particles can be controlled. Further, the method of reducing the substrate bias may be reduced stepwise or may be reduced continuously.

Conventionally, a method of controlling the growth of magnetic particles by applying a substrate bias has been known (for example, Japanese Patent Application Laid-Open No.
No. 98835). However, generally, since the substrate bias is kept constant, control of grain growth over the entire film thickness direction cannot be realized. This is because the degree of influence of the crystal orientation of the substrate or the underlayer or the degree of wettability with the sputtered material is different, and the conditions are different between the initial growth process immediately above the substrate or the underlayer and the subsequent growth process. . In addition, when the thickness of the magnetic thin film is increased and the magnetic particles form a layered structure, the state of the underlayer differs between the magnetic particles of each layer, so that the particle size distribution of the magnetic particles increases, and the uniformity of the entire film becomes uniform. And overwrite characteristics were further reduced. On the other hand, the method of controlling the substrate bias can control the growth of the magnetic particles, so that the problems of the related art can be solved.

Also in this method, the above-mentioned materials can be used as the material of the substrate, the magnetic particles, and the non-magnetic base material. As described above, in this method, the base layer may or may not be provided.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a magnetron sputtering apparatus used in the following examples. The sputtering chamber 1 is evacuated by an exhaust system 2, and a sputter gas is supplied to the sputtering chamber 1 from a gas supply system 3. Further, on a plurality of target holders (each having a magnet), a magnetic target 4, a base material target 5, and a base target 6 are set as sputtering sources, respectively. Power supplies 7, 8, and 9 are connected to these target holders, respectively. A substrate holder 10 is rotatably supported so as to face these targets, and a plurality of disk substrates 11 are rotatably supported on a peripheral portion of the substrate holder 10, and these disk substrates 11 are capable of rotating around themselves. ing. The revolution of the disk substrate 11 is controlled by the revolution control system 12. Further, an RF power source 13 for substrate bias is connected to the substrate holder 10. This RF power supply 13
Is operated during film formation, plasma is generated in the vicinity of the disk substrate 11 and ions in the plasma are accelerated and incident on the growing film surface, so that the surface movement of the sputtered substance on the disk substrate 11 is promoted. be able to.

Example 1-1 Co-20 at% Pt was provided as a magnetic target, and SiO ₂ was provided as a base material target. In the present embodiment, since the underlayer and the nonmagnetic base material are formed of SiO ₂ , the base target is not used, and the base material target is also used as the base target. Further, a glass disk substrate was set in the substrate holder. Seal the sputter chamber,
The evacuation system was operated to evacuate the inside of the sputtering chamber to 10 ^-6 Torr. By operating the gas supply system, Ar gas is
At a flow rate of sccm, the pressure in the sputtering chamber was set to 2 mT
orr. The substrate was caused to revolve by operating the revolution control system.

First, RF power was applied to the base material target to form a 50 nm thick SiO ₂ underlayer on the substrate. Next, with RF power applied to the base material target,
The application of DC current to the magnetic target was started, and the RF power supply for substrate bias was operated. In this way, a predetermined negative bias is applied to the substrate, RF plasma is generated near the substrate independently of the vicinity of the target, and ions in the plasma are incident on the substrate surface, thereby promoting the surface movement of the sputtered material on the substrate surface. Then, a magnetic thin film (granular film) having a thickness of 20 nm was formed on the underlayer. After that, stop supplying power to the magnetic target,
Forming a 10 nm thick SiO ₂ protective film on the magnetic thin film,
A magnetic recording medium was manufactured. The obtained magnetic recording medium was taken out of the sputtering chamber.

FIG. 2 is a cross-sectional TEM of the magnetic recording medium obtained.
The microstructure is shown by observation. An SiO ₂ underlayer 21 is formed on a substrate 11, and a magnetic thin film 22 is formed on the underlayer 21. The magnetic thin film 22, CoPt magnetic particles 2 SiO ₂ base material 22a adjacent to the SiO ₂ underlayer 21 having uniform and preferentially precipitated portion, the grain size at a given particle size
2b is composed of a portion uniformly dispersed in the SiO ₂ base material 22a, on which a SiO ₂ protective film 23 is further formed.

The magnetostatic properties of this magnetic recording medium were examined by VSM. As a result, the residual magnetization / film thickness product M _rt
Is 0.7 memu / cm ² and the coercive force Hc is 2500 O
e, the coercivity squareness ratio S ^* was 0.8.

The electromagnetic conversion characteristics of this magnetic recording medium were examined by a spin stand type disk evaluation device. As a result, even at a frequency of 200 kfci, the normalized medium noise per unit track is 0.01 μm ^1/2 μV
_rms / μV _pp .

Next, using a recording head having a recording magnetic pole Bs of 1.3 T and a track width of 1 μm, recording characteristics were examined at a flying height of 20 nm. In this case, when the recording current was 30 mA, the overwrite erasing ratio was a sufficient value of -45 dB. D ₅₀ values indicative of linear recording density performance 150kfc
i was exceeded.

Comparative Example 1-1 Co-20 at% Pt as a magnetic target, SiO _{2 as} a base material target, and Cr as a base target were set, and a glass disk substrate was set in a substrate holder. After applying DC power to the Cr underlayer target to form a Cr underlayer on the substrate, the RF
A magnetic recording medium was manufactured in the same manner as in Example 1-1, except that the input of power and the input of DC current to the magnetic target were simultaneously started.

FIG. 3 is a cross-sectional TEM of the magnetic recording medium obtained.
The microstructure is shown by observation. Cr underlayer 2 on substrate 11
4 is formed, and the magnetic thin film 22 is formed on the Cr underlayer 24. The magnetic thin film 22 has a Cr underlayer 24
CoPt magnetic particles 22a in a state of being directly connected to
And the spherical CoPt magnetic particles 22b
It consists of a portion dispersed in the iO ₂ base material 22a, on which a SiO ₂ protective film 23 is further formed. It is considered that the magnetic thin film 22 has the above fine structure for the following reasons. That is, the Cr underlayer 24
The wettability of CoPt is higher than that of SiO ₂ .
For this reason, when the sputtered substance is in the liquid phase state, first, CoPt preferentially precipitates on the Cr underlayer 24 and grows conically, and when the CoPt in the liquid phase decreases and exceeds the critical point, the conic SiO ₂ is deposited on the upper shaped for CoPt magnetic particles, further SiO ₂ in the liquid phase decreases and becomes less than the critical point when the spherical CoPt magnetic particles are precipitated and dispersed in the SiO ₂ matrix.

When the magnetostatic properties of this magnetic recording medium were examined, the product of residual magnetization and film thickness M _rt was 0.7 memu / cm.
^{2. The} coercive force Hc was 2000 Oe, and the coercive force squareness ratio S ^* was 0.65. It is considered that the reason why S ^* is lower than that in Example 1-1 is that two types of magnetic particles having different shapes are present. It is considered that the reason why Hc is lower than that in Example 1-1 is that the conical particles inhibit the growth of spherical particles.

When the electromagnetic conversion characteristics of this magnetic recording medium were examined, the normalized medium noise per unit track at a frequency of 200 kfci was 0.011 μm ^1/2 μV _rms / μ.
V _pp . The reason why the noise is slightly larger than that in Example 1-1 is that the conical particles connected to Cr are physically Si
It is considered that the separation by the O ₂ base material is due to the exchange coupling via the conduction electrons of Cr.

Next, the recording characteristics were examined at a flying height of 20 nm using a recording head having a recording magnetic pole Bs of 1.3 T and a track width of 1 μm in the same manner as in Example 1-1. Overwrite erase ratio is -35d
B. Although the recording characteristics are within the practical range,
Considerably inferior to -1. This is because although the coercive force is small and recording is easy, the magnetic field strength necessary for saturation recording is large because S ^* is low. The D ₅₀ value, which is an index of the linear recording density performance, is about 130 due to the low Hc.
kfci.

Comparative Example 1-2 In this example, an attempt was made to form a magnetic thin film directly on a Si disk substrate. As a result of preliminary experiments, when a magnetic thin film is formed directly on a Si disk
Since it was found that a sufficient coercive force could not be obtained at about nm, the thickness of the magnetic thin film was set to 50 nm. In this case, a magnetic recording medium was manufactured in the same manner as in Example 1-1, except that the underlayer was not formed.

FIG. 4 is a cross-sectional TEM image of the magnetic recording medium obtained.
The microstructure is shown by observation. Magnetic thin film 22 formed on the substrate 11, SiO ₂ base material 22 in proximity to the substrate 11
a was preferentially deposited, and a portion where approximately three layers of CoPt magnetic particles 22b having a small particle size were dispersed in the SiO ₂ base material 22a were laminated. Top CoPt
The particle size of the magnetic particles 22b was almost the same as that of Example 1-1, but the CoPt magnetic particles 2
The particle size of 2b was very small. In this case, SiO ₂ has higher wettability to the Si substrate than CoPt, so that SiO ₂ preferentially precipitates on the substrate in the initial stage of growth, but does not preferentially precipitate as in Example 1-1. Instead, CoPt particles begin to precipitate before SiO ₂ is sufficiently precipitated. As described above, since CoPt precipitates before the amount of CoPt in the liquid phase is sufficiently increased, the CoPt magnetic particles in the first layer have a very small particle size. Since SiO ₂ base material at this stage serve as a base, the second layer CoPt
The magnetic particles have a larger particle size than the first layer. Similarly, 3
The CoPt magnetic particles in the layer have a larger particle size than the second layer.

[0033] Examination of the static magnetic properties of the magnetic recording medium, residual magnetization, MakuAtsuseki M _rt is 1.2memu / cm
^{2. The} coercive force Hc was 2000 Oe, and the coercive force squareness ratio S ^* was 0.4. The fact that S ^* is very small is due to the fine structure as described above. When the thickness of the magnetic thin film is 5
Despite the thickness of 0 nm, _Mrt is not so large because the first layer of CoPt magnetic particles behaves superparamagnetically. Hc seems to be at the same level of 2500 Oe as that of Example 1-1 for the third layer, but the first layer and the second layer have the same Hc.
It becomes smaller due to the effect of the layer.

When the electromagnetic conversion characteristics of this magnetic recording medium were examined, the normalized medium noise per unit track at a frequency of 120 kfci was 0.01 μm ^1/2 μV _rms / μV.
less than _pp . Incidentally, the reason to lower the recording frequency can not be reduced M _rt as Example 1-1, due to the recording resolution is low.

Next, the recording characteristics were examined at a flying height of 20 nm using a recording head having a recording magnetic pole Bs of 1.3 T and a track width of 1 μm in the same manner as in Example 1-1. The recording current was 30 mA. Overwrite erase ratio is -25d
B and did not reach the practical range. This is because although the coercive force is small and recording is easy, the magnetic field strength required for saturation recording is large because S ^* is very low. D ₅₀ values indicative of linear recording density performance due to Hc is low, it was about 90Kfci.

Comparative Example 1-3 In this example, a magnetic recording medium was manufactured in the same manner as in Example 1-1 except that no substrate bias was applied. Also,
The thickness of the magnetic thin film was set to 50 nm as in Comparative Example 1-2.

FIG. 5 is a cross-sectional TEM of the magnetic recording medium obtained.
The microstructure is shown by observation. An SiO ₂ underlayer 21 is formed on a substrate 11, and a magnetic thin film 22 is formed thereon. Both the SiO ₂ base material 22a and the CoPt magnetic particles 22b are present in the portion of the magnetic thin film 22 that is in contact with the underlayer 21, and the CoPt dispersed in the SiO ₂ base material 22a is present.
The particle size of the magnetic particles 22b was very small, less than 5 nm. Thus, when the substrate bias is not applied,
Even if the same material is used for the base layer and the base material, magnetic particles are scattered on the base layer and a predetermined particle size cannot be obtained.

When the magnetostatic characteristics of this magnetic recording medium were examined, it was found to be superparamagnetic. For this reason, disk evaluation could not be performed. Example 2-1 A CoPt alloy target, a SiO ₂ target, and a 2.5-inch diameter glass substrate were installed in a magnetron sputtering apparatus. In an atmosphere of Ar gas at 2 mTorr, CoPt was applied while applying an RF bias of 600 W to the substrate.
A DC sputtering current of 0.5 A was applied to the alloy target, and an RF power of 600 W was applied to the SiO ₂ target to start dual simultaneous sputtering. While the simultaneous dual sputtering was continued for 7 minutes, an operation of applying a substrate bias of 600 W for only the first 2 minutes and then stopping was performed.
A magnetic thin film of nm was formed. Next, a carbon protective film was formed to a thickness of 10 nm on the magnetic thin film to produce a magnetic recording medium.

When the structure of this magnetic recording medium was observed by TEM in cross section, it was found that CoP having a particle size of about 6 nm was in contact with the substrate 11.
The t-magnetic particles 22b grew, and CoPt magnetic particles 22b having a particle size of 5 nm or less were generated thereon, and the periphery thereof was surrounded by the SiO ₂ base material 22a.

The magnetostatic properties and activation magnetic moment of the obtained magnetic recording medium were measured using a VSM. Hc
Is 1500Oe, M _rt was 0.35memu / cm ^2. Activation magnetic moment v _Isb is 0.06 × 10
^-14 emu.

Example 2-2 During the formation of the magnetic thin film, the substrate bias was set to 6 for the first 2 minutes.
A magnetic recording medium was manufactured in the same manner as in Example 2-1 except that the power was set to 00 W and then reduced to 400 W.

The structure of this magnetic recording medium was observed by TEM in cross section. As shown in FIG.
b had a particle size of about 9 nm and was larger than that of Example 2-1. Only one layer of coPt magnetic particles was present. Hc is 2000Oe, M _rt is 0.58memu / cm ^2, v
_Isb was 0.08 × 10 ^-14 emu.

Example 2-3 Example 1 was repeated except that a substrate bias was not applied for one minute at the time of forming a magnetic thin film, then a substrate bias of 600 W was applied for one minute, and then the substrate bias was reduced to 400 W. A magnetic recording medium was manufactured in the same manner as in 2-1.

The CoPt magnetic particles have a particle size of about 8 nm,
There was only one layer of oPt magnetic particles. Further, SiO ₂ was also interposed between the substrate and the layer of the magnetic particles, and the substrate and the magnetic particles were not in contact with each other. Hc is 2100 Oe, M
_rt is 0.55 memu / cm ² , v _Isb is 0.08 × 1
It was 0 ^-14 emu.

Example 2-4 While the simultaneous simultaneous sputtering of CoPt and SiO ₂ was continued for 12 minutes, the substrate bias was set to 600 W for the first 2 minutes, 400 W for the next 5 minutes, and then reduced to 300 W. Example 2 except that a magnetic thin film having a thickness of 32 nm was formed.
In the same manner as in -1, a magnetic recording medium was produced.

When the structure of this magnetic recording medium was observed by TEM in cross section, as shown in FIG.
The layer b has two layers. The first layer is in contact with the substrate, and the second layer has a structure in which the magnetic particles are laminated on the first layer of magnetic particles via the SiO ₂ base material 22a. The particle size of the CoPt magnetic particles was about 7 nm for both the first and second layers. Hc is 170
0 Oe, M _rt is 1.1 memu / cm ² , v _Isb is 0.1 memu / cm ² .
It was 09 × 10 ^-14 emu.

Example 2-5 While binary simultaneous sputtering of CoPt and SiO ₂ was continued for 12 minutes, the substrate bias was set to 600 W for the first 2 minutes, and then the substrate bias was gradually reduced to 0 W at the end of film formation. A magnetic recording medium was manufactured in the same manner as in Example 2-4, except that. In this case, columnar ellipsoidal particles were grown on the substrate so as to extend in the film thickness direction. H
c is 1900 Oe, M _rt is 1.2 memu / cm ² , v
_Isb was 0.15 × 10 ⁻¹⁴ emu.

Example 2-6 A magnetic recording medium was manufactured in the same manner as in Example 2-1 except that a 60 nm-thick Cr underlayer was formed before forming the magnetic thin film. The structure of the magnetic thin film was almost the same as that of Example 2-1. The particle size of the CoPt magnetic particles was about 7 nm. Hc is 2500Oe, M _rt is 0.55memu / c
m ² and v _Isb were 0.09 × 10 ⁻¹⁴ emu.

Comparative Example 2-1 A 60 nm Cr underlayer, a 10 nm metal magnetic thin film, and a 10 nm carbon protective film were formed on a substrate to produce a magnetic recording medium. The metal magnetic thin film on the Cr underlayer had a structure in which columnar magnetic particles grew and the magnetic particles were almost in contact with each other. Hc is 2500Oe, M _rt is 0.57m
emu / cm ² and v _Isb were 2.0 × 10 ⁻¹⁴ emu.

Comparative Example 2-2 A magnetic recording medium was manufactured in the same manner as in Example 2-1 except that a substrate bias of 400 W was continuously applied during the formation of the magnetic thin film. The formed magnetic thin film is structurally similar to that of Example 2-
1, but the particle size of the CoPt magnetic particles was 5 nm.
It was below. Hc is 1500Oe, M _rt is 0.52m
emu / cm ² and v _Isb were 0.06 × 10 ⁻¹⁴ emu.

When the above results are evaluated, the following can be said. Example 2-1 has a small film thickness, and _Mrt is comparative example 2
-2 smaller than the granular medium,
The coercive force Hc is almost the same as that of Comparative Example 2-2. Example 2
In No. 2, Hc was increased by about 500 Oe as compared with the granular medium of Comparative Example 2-2 because the grain growth was promoted. In Example 2-4, although the film thickness was large, the two-layer magnetic particles laminated in the film thickness direction had relatively large particle diameters.
Good three-dimensional dispersibility. Also, despite the magnetic particles being stacked, the activation magnetic moment v
_Isb has almost the same value as in the case where the magnetic particles have a single layer, which indicates that the dispersibility is good. Example 2
From the result of No. 5, it can be seen that even if the shape of the magnetic particles is made cylindrical or elliptical, it can be controlled so that the magnetostatic characteristics are hardly changed. In Example 2-6, since the crystal orientation of the magnetic thin film was improved by utilizing the crystallinity of the Cr underlayer, Hc was improved to 2500 Oe.

Next, the electromagnetic conversion characteristics of each magnetic recording medium were examined using a spin stand type disk evaluation device.
MIG head (gap length 0.3 μm, track width 4.0 μm) for recording, MR head (gap length 0.1
4 μm, track width 2.7 μm) and a flying height of 40 n
m. The normalized medium noise of a signal recorded at a recording density of 150 kfci was 0.015 in Examples 2-1 to 6-1.
０．０0.02 μm ^1/2 μV _rms / μV _pp , Comparative Example 2-2
0.02 μm ^1/2 μV _{rms in} (conventional granular media)
/ ΜV _pp , but the noise was relatively large in Comparative Example 2-1 (metal thin film medium) as 0.025 μm ^1/2 μV _rms / μV _pp .

Further, after recording at a recording density of 20 kfci, the overwrite erasing rate was measured when recording was performed at 80 kfci. All of the disks showed good values of -35 dB or more at a recording current of 20 mA. Example 2-4 shows that despite having a fine structure in which the magnetic particles are three-dimensionally dispersed in the film thickness direction, the overwrite characteristics are good and the dispersibility in the film thickness direction can be controlled. Was done. As described above, it was found that by controlling the substrate bias during film formation, a magnetic recording medium with low noise and excellent overwrite characteristics could be manufactured.

[0054]

As described in detail above, according to the present invention, magnetic recording with low noise, high resolution, controlled average particle size, small variation in particle size, optimized Hc, and improved S ^*. Media can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a sputtering apparatus used in an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the magnetic recording medium of Example 1-1.

FIG. 3 is a cross-sectional view of a magnetic recording medium of Comparative Example 1-1.

FIG. 4 is a sectional view of a magnetic recording medium of Comparative Example 1-2.

FIG. 5 is a sectional view of a magnetic recording medium of Comparative Example 1-3.

FIG. 6 is a sectional view of the magnetic recording medium of Example 2-2.

FIG. 7 is a sectional view of a magnetic recording medium of Example 2-4.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sputter chamber 2 ... Exhaust system 3 ... Gas supply system 4 ... Magnetic target 5 ... Base material target 6 ... Underlayer target 7, 8, 9 ... Power supply 10 ... Substrate holder 11 ... Disk substrate 12 ... Rotation / revolution control system 13 ... RF power supply 21, 24: Underlayer 22: Magnetic thin film, 22a: Non-magnetic base material, 22b: Magnetic particles 23: Protective film

Claims (3)

[Claims] 1. A magnetic recording medium having a base layer on a base material and a magnetic thin film in which magnetic particles are dispersed in a non-magnetic base material, wherein the base layer and the non-magnetic base material have the same main component. A magnetic recording medium having a structure in which a nonmagnetic matrix is selectively deposited on an underlayer, and magnetic particles and a nonmagnetic matrix are deposited thereon. 2. A method for manufacturing a magnetic recording medium having a base layer and a magnetic thin film in which magnetic particles are dispersed in a non-magnetic base material on a base material. While supplying the raw materials for the magnetic particles, the surface movement of the substance to be deposited on the underlayer is promoted, and the magnetic particles are deposited while the main component of the non-magnetic base material is preferentially deposited on the underlayer. A method for manufacturing a magnetic recording medium. 3. When manufacturing a magnetic recording medium having a magnetic thin film in which magnetic particles are dispersed in a non-magnetic base material on a base material, a substrate bias is applied when forming the magnetic thin film, and the substrate bias is applied during the film formation. A method for manufacturing a magnetic recording medium, characterized by reducing