JPH05109044A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a vertical magnetic recording medium wherein its recording medium noise is low and its recording and reproducing characteristic is excellent. CONSTITUTION:A vertical magnetic recording medium is formed in such a way that a magnetically soft layer 2, a magnetic layer 4, a protective layer 5 and the like are formed sequentially on a substrate 1. The vertical magnetic recording medium is constituted of a laminated body which is composed of a plurality of magnetically soft material layers via a nonmagnetic material intermediate layer 3. Permalloy or the like is used for the magnetically soft material layers. Carbon is used normally as a material for the nonmagnetic material layer. When the magnetically soft layers are constituted in this manner, the size of crystal lite for the magnetically soft material layers which affect the characteristic of the medium can be set at 300Angstrom or lower. As a result, it is possible to obtain the vertical magnetic recording medium whose medium noise can be lowered and whose recording and replay characteristic is excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a perpendicular magnetic recording medium comprising a soft magnetic layer, a magnetic layer and a protective layer, and particularly to a laminated body of a soft magnetic material layer having a plurality of soft magnetic layers and a non-magnetic material intermediate layer. The present invention relates to a perpendicular magnetic recording medium having low medium noise.

[0002]

2. Description of the Related Art In recent years, along with the widespread use of personal computers and the like, the demand for magnetic recording media used in hard disk drives has increased rapidly, and the demand for higher density magnetic recording media has increased. The perpendicular magnetic recording method is a magnetic recording method in which the direction in which the magnetic layer is magnetized is oriented in the direction perpendicular to the film surface of the magnetic layer, and the demagnetizing field inside the magnetic layer decreases during high-density recording, which is suitable for high density recording. .. A perpendicular magnetic recording medium for recording / reproducing by a perpendicular magnetic recording system has a soft magnetic layer such as a NiFe alloy formed as an underlayer on a non-magnetic substrate, and a CoC having perpendicular magnetic anisotropy formed thereon.
It has a structure in which a magnetic layer such as an r-based alloy and a protective layer such as carbon are sequentially formed. Usually, these underlayer, magnetic layer, and protective layer were formed by a method called sputtering, and each layer was formed as a single layer without being separated by an intermediate layer of another material. However, a normal perpendicular magnetic recording medium has a high medium noise, and a thin film magnetic recording medium formed by alternately laminating a magnetic film and a non-magnetic layer in order to reduce the medium noise (Japanese Patent Laid-Open No. Sho 63-63). -31331
7) is proposed.

[0003]

However, even the above-mentioned thin film magnetic recording medium has a problem that the medium noise is high and the recording / reproducing characteristics are poor. The present invention has been made in view of the above problems, and as a result of extensive studies on the cause of the medium noise, it was found that the configuration of the soft magnetic layer has a large influence on the medium noise, and the present invention is completed. I arrived.

[0004]

That is, the present invention is summarized as follows. In a perpendicular magnetic recording medium having a soft magnetic layer, a magnetic layer and a protective layer formed on a non-magnetic substrate, the soft magnetic layer is a laminated body composed of a plurality of soft magnetic material layers with a non-magnetic material intermediate layer interposed therebetween. A perpendicular magnetic recording medium characterized by the above.

[0005]

In the perpendicular magnetic recording medium of the present invention, the soft magnetic layer formed on the non-magnetic substrate is a laminate of a plurality of soft magnetic materials with the non-magnetic material intermediate layer interposed therebetween. The medium noise of the perpendicular magnetic recording medium is affected by the medium structure and the material and structure of the constituent material, but in the case of the perpendicular magnetic recording medium, the structure, material and structure of the soft magnetic layer on the non-magnetic substrate rather than the magnetic layer. Greatly affected by.

That is, when the soft magnetic layer is a laminate of a plurality of soft magnetic material layers with the non-magnetic material intermediate layer interposed therebetween, the crystal structure of the soft magnetic layer can be made a fine structure and the medium noise can be reduced. can do. When the soft magnetic material layer constituting the soft magnetic layer is a NiFe-based alloy and the crystallite size of the soft magnetic layer is a fine structure of 300 Å or less, noise can be reduced and good recording and reproducing characteristics can be obtained. A perpendicular magnetic recording medium can be obtained.

[0007]

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing a schematic structure of a perpendicular magnetic recording medium according to the present invention. Board 1
Is, for example, an aluminum substrate having a thickness of 1.27 mm, on which a non-magnetic material intermediate layer 3 (for example, a carbon layer 5 is formed).
The soft magnetic layer 6 composed of the two soft magnetic material layers 2 is formed via 0Å). The soft magnetic material layer has, for example, a thickness of 0.
It is a NiFe alloy of 5 μm. Then, this soft magnetic layer 6
A magnetic layer 4 is formed on top of this, and a protective layer 5 is further formed. For example, the magnetic layer is a 1000Å CoCrTa alloy layer and the protective layer is 250Å carbon.

As the non-magnetic substrate, it is usually possible to use a material such as aluminum, aluminum alloy, glass, ceramics, plastic, which has a high hardness, can easily provide smoothness and is excellent in corrosion resistance. In the case of aluminum or aluminum alloy, a substrate in which a plating film of NiP alloy or the like is formed on the non-magnetic substrate, a substrate in which the surface of the non-magnetic substrate is anodized, or the like is used. In the case of a glass substrate, crystallized glass or tempered glass is used. The non-magnetic substrate is finished to have a smooth surface by a chemical method, a mechanical method or a physical method.

The soft magnetic material layer is made of CuMoNiFe, Ni.
NiFe alloys such as FeNb, CoZ such as CoZrNb
A soft magnetic alloy having a high magnetic permeability such as r-based alloy, FeAl-based alloy, and MnZn ferrite can be used. If the coercive force of the soft magnetic material layer is smaller than 2 Oe, medium noise increases, and if it is larger than 10 Oe, the recording / reproducing output decreases, which is not preferable. Further, the total layer thickness of the soft magnetic material layer is preferably 2 μm or less because a thick layer tends to cause distortion in the perpendicular magnetic recording medium. In the case of a NiFe-based alloy, the optimum composition is 60 to 90% by weight of Ni.

When the material of the soft magnetic material layer is a NiFe type alloy, if the crystallite size of this alloy is larger than 300Å, the structure of the soft magnetic layer does not become a fine structure, which is not preferable because the noise is large.

The non-magnetic material intermediate layer forming the laminated body may be made of a non-magnetic alloy such as carbon, Ti, Cr and Ge. A suitable thickness of the intermediate layer is around 50Å. The number of soft magnetic material layers is preferably a soft magnetic layer in which 1 to 20 soft magnetic material layers are laminated with a nonmagnetic material intermediate layer interposed therebetween.
A nonmagnetic alloy layer of Ti, Cr or the like may be formed between the nonmagnetic substrate and the soft magnetic layer in order to improve the adhesion between the nonmagnetic substrate and the soft magnetic layer.

The material of the magnetic layer is CoCrTa or Co.
A Co-based alloy or a ferrite-based alloy having perpendicular magnetic anisotropy such as Cr or CoCrPt can be used. The protective layer is usually
It is formed of carbon, oxides, nitrides, carbides of Si, Zr, Hf, Cr and the like. Further, in order to improve the lubricity of the protective film, a lubricating layer may be formed on the surface of the protective film.

Example 1 On a smooth glass substrate having an outer diameter of 95 mm, an inner diameter of 25 mm, and a thickness of 1.27 mm, a soft magnetic layer was used as a nonmagnetic material intermediate layer with a carbon layer (50 Å) interposed between them to form a layer of 0.5 μm.
Two soft magnetic material layers of m ₈₀ of Ni ₈₀ Fe ₂₀ (hereinafter, the composition formula of the soft magnetic material layer is shown by weight%) are laminated to have a thickness of 1.00
A 5 μm soft magnetic layer was formed. A perpendicular magnetic recording layer of CoCrTa and a protective layer of carbon were sequentially formed thereon to prepare a perpendicular magnetic recording medium (Experiment No. 1). Similarly, four layers of Ni ₈₀ Fe ₂₀ soft magnetic material layers of 0.25 μm each having the above-described structure were laminated to prepare a laminated body having a thickness of 2.015 μm (Experiment No. 2). Further, the soft magnetic material layer Cu _{3. 5} Mo _4.
5 One layer of Ni ₇₇ Fe _{15 with} 0.5 μm soft magnetic material layer
A layer (Experiment No. 3) and a soft magnetic material layer of 0.05 .mu.m having 20 layers were prepared (Experiment No. 4). Table 1 shows the measurement results of the crystallite size of the soft magnetic material layer of these media, the coercive force, and the media noise during reproduction of the media. The crystallite measuring method, the coercive force measuring method, and the medium noise during reproduction were measured as follows.

(Method of Measuring Crystallite of Soft Magnetic Material Layer) A soft magnetic layer was formed on a non-magnetic substrate, and the X-ray diffraction intensity of the soft magnetic material layer was measured by using an X-ray diffractometer. From the diffraction intensity, the Bragg angle θ of the diffraction line on the Ni (111) plane
(Degree), the integral width β (radian), and these values
Substituting in Scherrer's equation D = λ / (β × cos θ), the crystallite size D is obtained. However, λ is the measurement X
This is the wavelength of the line, and was set to 1.54 in this experiment.

(Method of measuring coercive force) A soft magnetic layer was formed on a non-magnetic substrate, and the non-magnetic substrate on which the soft magnetic layer was formed was punched into a square of 7 mm square and the coercive force was measured. The device is
A vibration sample type automatic recording device MODEL BHV-3.5 manufactured by Riken Denshi Co., Ltd. was used.

(Method of measuring medium noise during reproduction) A reproduction spectrum when a signal having a linear recording density of 45 kfci is recorded on a perpendicular magnetic recording medium in which a soft magnetic layer, a magnetic layer and a protective layer are sequentially formed on a non-magnetic substrate. The difference from the system noise spectrum was obtained as the medium noise.

Example 2 A perpendicular magnetic recording medium was prepared by the same procedure as Experiment No. 2 or No. 4 of Example 1 except that the material of the non-magnetic material intermediate layer formed between the soft magnetic material layers was Ti. (Experiment No5, No6). With respect to the obtained perpendicular magnetic recording medium, the measurement results of the crystallite size of the soft magnetic material layer, the coercive force and the medium noise at the time of reproduction were measured by the measuring method of Example 1. The results are shown in Table 1.

[Comparative Example] Ni ₈₀ Fe ₂₀ layer thickness on a smooth glass substrate having an outer diameter of 95 mm, an inner diameter of 25 mm and a thickness of 1.27 mm.
A soft magnetic material layer of 1.0 μm was formed as a soft magnetic layer. A perpendicular magnetic recording layer of CoCrTa and a protective layer of carbon were sequentially formed thereon to prepare a perpendicular magnetic recording medium (Experiment No.
1). Similarly, with the above-mentioned structure, the soft magnetic material layer is made of Cu _3.5 M.
o _{4. 5} Ni ₇₇ as the coercive force of 2Oe the composition of Fe ₁₅ (Experiment No2) to that of 10Oe coercive force (Experiment No
3) and were created. Table 1 shows the results of measuring the crystallite size of the soft magnetic material layer, the coercive force, and the medium noise at the time of reproduction of the obtained perpendicular magnetic recording medium by the method of the example.

[0019]

According to the present invention, since the soft magnetic layer formed on the non-magnetic substrate is a laminated body composed of a plurality of soft magnetic material layers with the non-magnetic material intermediate layer interposed therebetween, the medium noise is low, A perpendicular magnetic recording medium having excellent recording / reproducing characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a perpendicular magnetic recording medium showing an example of the present invention.

FIG. 2 is a sectional view of a perpendicular magnetic recording medium showing an example of the present invention.

[Explanation of symbols]

 1: Non-magnetic substrate 2: Soft magnetic material layer 3: Non-magnetic material intermediate layer 4: Magnetic layer 5: Protective layer 6: Soft magnetic layer

[Table 1]

Claims (4)

[Claims] 1. A perpendicular magnetic recording medium comprising a soft magnetic layer, a magnetic layer and a protective layer formed on a non-magnetic substrate, wherein the soft magnetic layer comprises a plurality of soft magnetic material layers with a non-magnetic material intermediate layer interposed therebetween. A perpendicular magnetic recording medium, which is a laminated body made of. 2. The perpendicular magnetic recording medium according to claim 1, wherein the soft magnetic material layer is a NiFe alloy and the crystallite size of the soft magnetic layer is 300 Å or less. 3. The perpendicular magnetic recording medium according to claim 2, wherein the non-magnetic material intermediate layer is carbon. 4. The perpendicular magnetic recording medium according to claim 3, wherein the non-magnetic substrate is glass.