JPH10125520A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise charging rate of magnetic powder and eliminate unevenness of a medium surface by forming a non-magnetic base material of an organic matter and forming a shape of magnetic particle to a sphere, a prolate spheroid, an oblate spheroid, a cone, a frustum of circular cone and a column. SOLUTION: In a magnetic thin film 10, magnetic particle 12 dispersed in to a non-magnetic base material 11 consisting of an organic matter is formed to a sphere, a prolate spheroid, an oblate spheroid, a cone, a frustum of circular cone and a column. Furthermore, hardness of the non-magnetic base material 11 is made lower than hardness of the magnetic particle 12. Such a magnetic recording medium 10 is formed by a method such as binary simultaneous sputter or alternating sputter by using a magnetic metallic target and an organic matter target on a substrate 3. Thereby, charging rate of magnetic powder is raised, unevenness of a medium surface is eliminated and a magnetic recording medium which is excellent in medium S/N characteristic, sliding characteristic with a head and weather proof is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium.

[0002]

2. Description of the Related Art In order to increase the recording density in magnetic recording, a magnetic recording medium capable of high S / N recording is required. In response to this, a magnetic particle-dispersed magnetic recording medium having a magnetic thin film having a structure in which magnetic particles are dispersed in a nonmagnetic base material made of an inorganic material has been developed (19th Annual Meeting of the Japan Society of Applied Magnetics). Meeting Summary (1996) 390). In such a magnetic particle dispersion type magnetic recording medium,
Since the magnetic exchange coupling of the magnetic particles is separated by the non-magnetic base material, the medium noise is reduced.

However, when a non-magnetic base material made of an inorganic material is used, there is a problem that the magnetic particles easily react with the non-magnetic base material and the magnetic characteristics of the magnetic particles are easily impaired. In addition, the non-magnetic base material made of an inorganic material has high hardness, and when used without providing a protective film that causes a spacing loss between the medium and the head, the head is not operated during a CSS (contact start and stop) operation or a contact operation. When the collision occurs, there is a problem that the wear of the head is accelerated. In order to avoid this problem, it is necessary to finish the medium with extremely high flatness.

On the other hand, in a conventionally known coating type magnetic recording medium, a magnetic thin film in which magnetic particles are bound with an organic binder is used (IEEE Trans. Mag).
n. , MAG-21, 5, p. 1480 (1985)). A coating type magnetic recording medium is obtained by mixing needle-like or hexagonal plate-like crystalline magnetic particles and a liquid organic binder, applying the mixture on a substrate by a spin coating method, a dipping method, and then solidifying the binder. Manufactured. Such a coating type magnetic recording medium has a low reproduction signal due to a low filling rate of magnetic particles, and it is difficult to perform low flying or contact operation of a head due to unevenness of the medium surface when the binder is solidified. There is a problem of.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a high medium S / N ratio while avoiding deterioration of noise characteristics caused by a reaction between a non-magnetic base material and magnetic particles. An object of the present invention is to provide a magnetic recording medium capable of suppressing wear of a head even when performing a head contact recording / reproducing operation.

[0006]

According to the present invention, there is provided a magnetic recording medium having a magnetic thin film in which magnetic particles are dispersed in a non-magnetic base material, wherein the non-magnetic base material is made of an organic substance, It is characterized in that the shape of the particles is spherical, oblate spheroidal, flat spheroidal, conical, truncated conical or cylindrical.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The magnetic recording medium of the present invention has a structure in which a magnetic thin film is formed on a substrate. Further, an underlayer and a magnetic thin film may be formed on the substrate. This underlayer is provided for controlling the crystal orientation of the magnetic thin film. The magnetic thin film constituting the magnetic recording medium of the present invention has a structure in which magnetic metal particles are dispersed in a non-magnetic base material.

Examples of the organic substance used for the non-magnetic base material constituting the magnetic thin film of the magnetic recording medium of the present invention include polytetrafluoroethylene, a C-F plasma polymer, and polyimide.

The magnetic particles constituting the magnetic thin film of the magnetic recording medium of the present invention are preferably made of a magnetic metal having a large saturation magnetization and a large crystal magnetic anisotropy. The larger the crystal magnetic anisotropy of the magnetic particles, the more stable the recorded information and the larger the signal output, which is preferable.

[0010] From such a viewpoint, as a magnetic metal,
It is preferable to use at least one selected from the group consisting of Co, Pt, Sm, Fe, Ni, Cr, Mn, Bi and Al, and alloys thereof. Among them, CoPt and SmC having large crystal magnetic anisotropy
Particularly preferred are Co-based alloys such as o and CoCr, and Mn alloys such as MnBi and MnAl having a large magnetic anisotropy energy. Fe and / or Ni may be added to these metals or alloys for the purpose of controlling magnetic properties.
In order to improve magnetic properties of these metals or alloys, Cr, Nb, V, Ta, Ti, W, Hf, In, Si,
Elements such as B may be added.

In the magnetic thin film according to the present invention, the shape of the magnetic particles dispersed in the nonmagnetic base material made of an organic material is spherical, oblate spheroidal, flat spheroidal, conical,
It is frustoconical or cylindrical. The size of the magnetic particles in the non-magnetic base material is preferably 10 to 20 nm. The filling ratio of the magnetic particles in the non-magnetic base material is 50 to 70 vol%.
It is preferred that The hardness of the magnetic particles (Vickers hardness) is about 700 kg / mm ² , but the hardness of the non-magnetic base material is lower than the hardness of the magnetic particles,
It is preferably 0 kg / mm ² .

In the conventional coating type medium, the size of the magnetic particles is about 50 nm and the filling rate of the magnetic particles is about 40 vol%, so that the magnetic particles in the magnetic thin film according to the present invention are coated in terms of size and filling rate. Significantly different from medium. For this reason, the magnetic recording medium of the present invention exhibits high coercive force (high Hc) and low remanent magnetization (low Mr) as magnetostatic characteristics, and as a result, a large reproduction signal and medium noise (S / Nm) are obtained as electromagnetic conversion characteristics. Can be

The magnetic recording medium of the present invention can be manufactured by simultaneously or alternately depositing a magnetic metal and an organic substance on a substrate in a gas phase by the following method.
For example, a method of dual simultaneous or alternate sputtering using a magnetic metal target and an organic target on a substrate; or a method in which a magnetic metal is sputtered or vapor-deposited on a substrate in a rare gas containing a fluorinated hydrocarbon gas, A method of plasma polymerizing a hydrogenated hydrocarbon gas,
And the like. Examples of the hydrocarbon gas used in the latter method include CF ₄ , CHF ₃ , CHF ₂ , CH ₄ or C ₂ H ₄ or a mixed gas thereof. Further, an organic substance may be deposited.

Since the magnetic recording medium of the present invention has a structure in which magnetic particles are dispersed in a non-magnetic base material made of an organic substance, the magnetic particles hardly react with the non-magnetic base material, and the magnetic recording medium has a lower magnetic thin film. Shows high weather resistance with noise. In addition, since the non-magnetic base material made of an organic material has a lower hardness and elasticity than magnetic particles, has a lubricating effect, and has good lubricity and wettability of the lubricant, it performs the CSS operation and the head contact recording / reproducing operation. However, wear of the head can be suppressed.

[0015]

Embodiments of the present invention will be described below. Embodiment 1 FIG. 1 schematically shows a sputtering apparatus used for forming a magnetic recording medium of the present embodiment. In FIG. 1, a substrate pallet 2 is rotatably provided in a vacuum chamber 1, and a substrate 3 is set on the substrate pallet 2.
Further, a CoPt target 4 and a polytetrafluoroethylene (PTFE) target 5 are provided in the vacuum chamber 1 so as to face the substrate 3.

The magnetic recording medium of this embodiment was manufactured as follows using the apparatus shown in FIG. After the inside of the vacuum chamber 1 was evacuated to a degree of vacuum higher than 5 × 10 ⁻⁵ Pa by a cryopump, Ar gas was introduced at a flow rate of 100 sccm to adjust the pressure in the vacuum chamber 1 to 0.6 Pa. While rotating the substrate pallet 2 on which the disk-shaped substrate 3 is mounted at 200 rpm, a DC is applied to the opposing CoPt target 4.
A magnetic thin film was formed on the surface of the substrate 3 by supplying power of 50 W and RF 500 W to the PTFE target 5 and discharging.

FIG. 2 shows a magnetic recording medium (Example 1) manufactured as described above. As shown in FIG.
The magnetic thin film 10 formed on the surface has a structure in which spherical CoPt magnetic particles 12 having an average particle diameter of about 10 nm are dispersed in a PTFE base material 11.

For comparison, in FIG. 1, a magnetic thin film was formed on the substrate 3 in the same manner as described above, using an SiO ₂ target instead of the PTFE target. The magnetic thin film thus formed had the same structure as that of FIG. 2 except that the base material was SiO ₂ . A lubricant was applied to a thickness of 1 nm on the magnetic thin film. This magnetic recording medium is referred to as Comparative Example 1.

For comparison, the average particle size is 0.05 μm.
m of Ba ferrite magnetic particles were mixed with an organic binder, applied to a glass disk substrate to a thickness of 0.2 μm by a spin coating method, and pressure was applied by a calendar roll to solidify the organic binder. This magnetic recording medium is referred to as Comparative Example 2.

The structures of the magnetic thin films of these magnetic recording media were examined by analytical TEM. As a result, in Comparative Example 1, Co
A small amount of Co oxide was generated around the Pt magnetic particles. In contrast, in Example 1 and Comparative Example 2, the non-magnetic base material and the magnetic particles were clearly separated, and there was no substance interposed at the interface between them.

Next, the magnetostatic properties of these magnetic recording media were measured by a vibrating sample magnetometer (VMS). Table 1 shows values of the coercive force Hc, (residual magnetization) × (film thickness) _Mrt , and coercive force squareness ratio S ^* . Also, using a thin film head against these magnetic recording media examined R / W characteristics were examined medium S / N at a recording density D _70. The results are also shown in Table 1.

[0022]

[Table 1]

As it is apparent from Table 1, the recording medium of Example 1, Hc, shows good values in all M _r t and S ^*, it can be seen that the high recording resolution and low noise characteristics can be obtained.

Further, regarding these magnetic recording media,
The sliding characteristics were examined as follows. That is, the disk was rotated at 300 rpm, and the Si ₃ N ₄
The pin was pressed with a load of mgf to check the degree of wear of the pin. As a result, in Comparative Example 1, the pin slipped by 0.02 μm after 3 days. On the other hand, in Example 1, neither the disk nor the pin was worn down at all even after three days.

Embodiment 2 In this embodiment, a base film is formed on a substrate, and a magnetic thin film having a structure in which spherical CoPt magnetic particles are dispersed in a PTFE base material is formed in the same manner as in Embodiment 1. Thus, a magnetic recording medium was manufactured.

When a Cr underlayer is formed, CoPt magnetic particles in the PTFE base material are conical when the underlayer thickness is about 3 nm, and CoPt magnetic particles in the PTFE base material when the underlayer thickness is about 5 nm. The particles became frustoconical. When the V underlayer was formed, the CoPt magnetic particles in the PTFE base material became cylindrical.

Further, all the magnetic recording media exhibited better characteristics than the conventional magnetic recording media. Example 3 A disk-type substrate was set on a substrate pallet rotatably provided in a vacuum chamber, and a CoPt target was provided so as to face the substrate. In addition, a high-frequency coil was connected between the substrate and the target.

The inside of the vacuum chamber is evacuated to a degree of vacuum of 5 × 10 ⁻⁵ Pa, and Ar is 180 sccm and CF ₄ is 40 scc.
The CoPt target was discharged at DC 100 W while rotating the substrate pallet at a flow rate of m, and an alternating current of 40 kHz was passed through the high-frequency coil to form a magnetic thin film on the disk substrate. The formed magnetic thin film had a structure in which flat spheroidal CoPt magnetic particles were dispersed in a base material composed of a CF plasma polymer. This magnetic recording medium also exhibited high recording resolution and low noise characteristics as in Example 1, and also had excellent sliding resistance.

[0029]

As described above in detail, according to the present invention, a magnetic recording medium having excellent medium S / N characteristics, sliding characteristics with a head, and weather resistance can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a sputtering apparatus used for manufacturing a magnetic recording medium of the present invention.

FIG. 2 is a sectional view schematically showing a magnetic recording medium according to the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber 2 ... Substrate pallet 3 ... Substrate 4 ... CoPt target 5 ... PTFE target 10 ... Magnetic thin film 11 ... PTFE base material 12 ... CoPt magnetic particles

Claims (3)

[Claims] 1. A magnetic recording medium having a magnetic thin film in which magnetic particles are dispersed in a non-magnetic base material, wherein the non-magnetic base material is made of an organic substance, and the shape of the magnetic particles is spherical, oblate spheroidal. A magnetic recording medium having a shape of a flat spheroid, a cone, a truncated cone, or a column. 2. The magnetic recording medium according to claim 1, wherein the hardness of the non-magnetic base material is lower than the hardness of the magnetic particles. 3. The magnetic recording medium according to claim 1, wherein the magnetic thin film in which magnetic particles are dispersed in a non-magnetic base material is formed by sputtering a magnetic material target and an organic target.