JPH04182925A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain satisfactory electromagnetic transducing characteristics by forming a nonmagnetic underlayer on a nonmagnetic substrate such as a glass substrate so that the axis of easy magnetization of a magnetic layer as an upper layer is oriented in the circumferential direction. CONSTITUTION:A glass substrate 1 with a smooth surface and a target 2 are placed opposite to each other and a mask 3 with a central circular hole 3a is set between the substrate 1 and the target 2. Particles evaporated from the target 2 by magnetron sputtering are deposited on the substrate 1 through the imaginary center line 4 of the substrate 1 to form a nonmagnetic underlayer 5 and a magnetic layer 6 is formed on the underlayer 5 without using a mask. A carbon layer as a protective layer is then formed on the magnetic layer 6 to produce a magnetic disk. Satisfactory electromagnetic transducing characteristics are obtd.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to magnetic recording media such as magnetic disks.

(Prior Art) The general structure of a magnetic recording medium is to form a non-magnetic underlayer such as Cr on a non-magnetic substrate, and coat the Co-magnetic underlayer on this non-magnetic underlayer.
A magnetic layer made of Ni or the like is formed, and a protective layer made of carbon or the like is formed on this magnetic layer.

Conventionally, the above-mentioned non-magnetic substrate includes a NiP plated aluminum plate and a glass substrate.

(Problem to be Solved by the Invention) In the case of an aluminum plate plated with NiP, the surface is textured to align the axis of easy magnetization in the circumferential direction, thereby improving electromagnetic conversion characteristics. .

However, in order to achieve high density in magnetic disk drives, it is important to lower the flying height of the head.For lower flying height, the closer the disk surface is to a mirror surface, the better.If there is even a slight protrusion, the head The possibility of a crash is much greater. Therefore, when texture processing is applied, the surface roughness increases, making it impossible to lower the flying height of the head.

On the other hand, when a glass substrate is used as the nonmagnetic substrate, surface smoothness can be obtained, but sufficient electromagnetic conversion characteristics cannot be obtained because magnetic alignment treatment cannot be performed.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides an arrangement in which the axis of easy magnetization of the upper magnetic layer is in the circumferential direction on a non-magnetic substrate such as a glass substrate having a surface roughness Ra of, for example, 2OA or less. A nonmagnetic underlayer was formed so as to be oriented, and a magnetic layer and a protective layer were sequentially formed on this underlayer.

(Function) When forming a nonmagnetic underlayer by sputtering, the evaporated particles from the target cross the virtual center line of the substrate and reach the substrate, thereby increasing the magnetization of the magnetic layer formed on the nonmagnetic underlayer. The easy axis is oriented circumferentially.

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in Fig. 1, a glass substrate 1 with a surface roughness Ra of 20A or less and a target 2 are placed facing each other, and a circular hole 3a is provided in the center between the glass substrate 1 and the target 2.
A mask 3 on which a non-magnetic underlayer 5 is formed is arranged, and evaporated particles from the target 2 are caused to fly over the virtual center line 4 of the substrate 1 and adhere to the substrate 1 by magnetron sputtering, thereby forming a non-magnetic underlayer 5. A magnetic layer 6 is formed on one side of the non-magnetic underlayer 5 using a mask.

Here, as the non-magnetic underlayer 5 formed by the above-mentioned shielding mask process, a Cr layer with a thickness of 5,200 layers is used.
With R=27 mm, the magnetic layer 6 formed on this Cr layer without using a shielding mask process is as follows.
C0t9.5Crt. 4Ta,sP ta,o a
t % was set to 400 layers, and a carbon layer was formed as a protective layer on the Conomagnetic layer 6 by 250 layers to produce a magnetic disk.

1. On a glass substrate with a surface roughness of Ra or less than 2OA, a Cr layer as an underlayer is formed by the usual method under the same conditions as the example medium, and a magnetic layer is formed on this Cr layer under the same conditions as the actual medium. A magnetic disk with a protective layer formed thereon was manufactured.

Le cunning five! Texture treatment was applied to a nonmagnetic substrate consisting of an aluminum substrate with NLP plating (-1).A magnetic disk was produced by forming the same nonmagnetic underlayer and magnetic layer as above on this substrate.

In the texture treatment, a WA4000 polishing tape was used, and after the carbon film was formed, burnishing was performed with a GC8000 polishing tape.

First, the results of measuring the hysteresis loop for the above-mentioned example medium and comparative example medium 1 are shown in Figure 2 (a) and (b).
The measurement results of the magnetostatic properties are as shown in the following 1st
Now shown in the table.

In the same table, Tan is measured by applying an external magnetic field in the circumferential direction, and Rad is measured by applying an external magnetic field in the radial direction.

Table 1 As is clear from these measurement results, the easy axis of magnetization in the example medium is oriented in the circumferential direction, whereas in the comparative example medium 1, Tan and Rad overlap, and the easy axis of magnetization is isotropic. It is true.

Next, for the example medium and comparative example medium 2, the number of hits with the head at each flying height was measured, and the results are shown in FIG.

As is clear from this measurement result, the example medium can cope with low flying heights up to a flying height of 0.055 μm without hitting, whereas the comparative example medium 2 can cope with a flying height of 0.055 μm.
It hits at 8μm and cannot handle low flying heights. That is, the surface roughness Ra of the example medium is 11 people, whereas the surface roughness Ra of the comparative example medium 2 is 85A, and the surface roughness R
It can be seen that unless a is small, it is not possible to cope with low flying height.

Next, the results of electromagnetic conversion measurements for the example medium and comparative example medium 2 are shown in Table 2, and the measurement results of the output, S/N ratio, and CZN ratio when recording a 10 MHz signal are shown in Table 3.
Now shown in the table.

The head specifications and measurement conditions used in the measurements are as follows.

Track width = 8μm Number of turns = 50 Gap length:
0.3μm ABS: 270μm Flying height: 0.05μm
m at6.5m/secR=27mm
2691 rpmHF=5MHz LF=1.
88MHzAs is clear from these measurement results, the example medium is superior to comparative example medium 2,
Easily adaptable to high density.

Table 2-1 Table 2-2 Table 3 (Effects of the Invention) As explained above, according to the present invention, an upper layer and A non-magnetic underlayer is formed so that the axis of easy magnetization of the magnetic layer is oriented in the circumferential direction, and a magnetic layer and a protective layer are sequentially formed on this underlayer, resulting in surface smoothness and low head performance. It can cope with levitation, and since the axis of easy magnetization is oriented in the circumferential direction, sufficient electromagnetic conversion characteristics can be obtained.

[Brief explanation of the drawing]

1, 2(a) and 2(b) are diagrams showing the hysteresis loops of the example medium according to the present invention and the comparative example medium, and FIG. 3 is the diagram showing the hysteresis loop of the same example medium and another comparative example. 7 is a graph showing a relationship between a head flying height of a medium and a glide count. DESCRIPTION OF SYMBOLS 1...Nonmagnetic substrate, 2...Target, 3...Mask, 5...Nonmagnetic base layer, 6...Magnetic layer.

Claims (1)

[Claims] In a magnetic recording medium in which a nonmagnetic underlayer, a magnetic layer, and a protective layer are sequentially formed on a nonmagnetic substrate, the nonmagnetic substrate is a substrate with an extremely smooth surface such as a glass substrate, and the magnetic layer is easily magnetized. A magnetic recording medium characterized in that an axis is oriented in the circumferential direction.