JPH05258305A - Production of perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To avoid the crushing of a magnetic head as well as to orient the axes of easy magnetization of the soft magnetic layer of a magnetic recording medium in the radial directions of the medium without grooving the substrate, to prevent reduction and change in permeability and to also prevent reduction and change in reproduction output. CONSTITUTION:A soft magnetic layer 22 is formed on a substrate 21 by plating in a plating bath with an anode magnetized beforehand by impressing a magnetic field from the center of the substrate 21 toward the radial direction. The axes 24 of easy magnetization of the soft magnetic layer 22 can be oriented in the radial directions of the resulting magnetic recording medium.

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 in which a soft magnetic layer, a perpendicular magnetic layer, a protective layer and the like are provided on a disk-shaped substrate and a method for manufacturing the same, and more particularly to a perpendicular magnetic recording medium affected by an external magnetic field. The present invention relates to a hardened perpendicular magnetic recording medium and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for improvement in recording density for recording media, but the perpendicular magnetic recording technology has been attracting attention because it can increase the recording density as compared with in-plane magnetic recording. Technology.

FIG. 6 is a schematic view showing a recording method of this perpendicular magnetic recording. Magnetic head 1 on perpendicular magnetic recording medium 2
Are arranged so as to float at appropriate intervals. Medium 2
The soft magnetic layer 4 is formed on the substrate 3, and the perpendicular magnetization layer 5 is formed on the soft magnetic layer 4. A protective layer (not shown) is usually formed on the perpendicular magnetization layer 5. On the other hand, the magnetic head 1 has a main magnetic pole 6 and an auxiliary magnetic pole 7. Then, the magnetic flux 8 generated from the main magnetic pole 6 vertically enters the medium surface and vertically passes through the perpendicular magnetization layer 5,
The soft magnetic layer 4 is reached. Then, the magnetic flux 8 extends through the soft magnetic layer 4 along the medium surface, passes through the perpendicular magnetic layer 5 again at the position of the auxiliary magnetic pole 7 of the magnetic head 1, and returns to the auxiliary magnetic pole 7. Thereby, from the main magnetic pole 6, the perpendicular magnetization layer 5, the soft magnetic layer 4,
A magnetic circuit is formed that returns to the main magnetic pole 6 through the perpendicular magnetization layer 5 and the auxiliary magnetic pole 7. Then, the main pole 6 of the perpendicular magnetization layer 5
Is magnetized in the thickness direction of the layer, that is, in the perpendicular direction, and perpendicular magnetic recording is performed.

Thus, in the conventional perpendicular magnetic recording medium, a soft magnetic layer is formed by sputtering Permalloy or the like on the surface of a substrate, and then a magnetic layer (perpendicular magnetic layer) is similarly formed by sputtering. It is manufactured through the necessary steps. However, in this conventional manufacturing method, due to the convenience of the sputtering process, as shown in FIG. 7, the easy magnetization axis 9 of the soft magnetic layer 4 is oriented in one direction, or
Alternatively, as shown in FIG. 8, the easy axis 10 is easily magnetized in the circumferential direction of the substrate. As described above, when the easy axis 9 of the soft magnetic layer 4 is oriented in one direction (FIG. 7), the magnetic permeability of the soft magnetic layer 4 varies depending on the position in the circumferential direction of the medium, and the level of the reproduction signal periodically changes. It fluctuates. On the other hand, if the easy magnetization axis 10 of the soft magnetic layer 4 is oriented in the circumferential direction of the medium (FIG. 8), the magnetic permeability of the soft magnetic layer 4 becomes low throughout the medium. Therefore, the reproduction level is always low regardless of the position in the circumferential direction. Further, during recording / reproduction, the reproduction output is significantly reduced due to the influence of a slight external magnetization from the vertical direction.

Therefore, in order to solve the problem caused by the orientation of the easy axis of magnetization of the soft magnetic layer, a large number of grooves extending in the radial direction are formed on the surface of the substrate 3a as shown in FIG. A technique for orienting the easy axis of magnetization in the radial direction of the soft magnetic layer has been proposed (Japanese Patent Laid-Open No. 2-126421).

[0006]

However, this conventional technique requires a step of forming tens to hundreds of grooves having a depth of 100 to 1000Å in the radial direction of the substrate, which complicates the manufacturing process. become. Further, since the relative movement direction of the magnetic recording medium and the magnetic head is a direction orthogonal to the groove, due to the unevenness in the circumferential direction generated along with the formation of the groove,
There is a problem that the magnetic head crashes or the friction coefficient of the magnetic disk becomes high, so that the durability of the magnetic recording medium is significantly lowered.

The present invention has been made in view of the above problems, and it is possible to effectively prevent the level fluctuation of the reproduction output,
An object of the present invention is to provide a perpendicular magnetic recording medium that can suppress the influence of an external magnetic field on the reproduction output to a sufficiently small level and that has excellent durability, and a method for manufacturing the same.

[0008]

A method of manufacturing a perpendicular magnetic recording medium according to the present invention uses an anode obtained by previously magnetizing a disk-shaped substrate by applying a magnetic field corresponding to the radial direction of the substrate. A step of immersing in a plating bath, plating a surface of the substrate with a soft magnetic layer having an easy axis of magnetization oriented in the radial direction of the substrate, and forming a perpendicular magnetic layer on the soft magnetic layer. It is characterized by.

[0009]

In the present invention, a disk-shaped substrate is immersed in a plating bath using an anode magnetized by applying a magnetic field corresponding to the radial direction of the substrate in advance to form a soft magnetic layer. Since the anode to which a magnetic field extending in the radial direction is previously applied to the substrate is used, the easy axis of magnetization of the soft magnetic layer formed by plating is oriented in the radial direction of the substrate. Therefore, since the easy axis of magnetization of the soft magnetic layer is perpendicular to the relative moving direction of the magnetic head and the medium, the magnetic permeability does not fluctuate and a high-level reproduction signal can be obtained constantly. Further, even if a vertical external magnetic field is applied to the medium, it is possible to prevent the reproduction signal from decreasing.

Since no radial groove is formed on the substrate of the present invention, the magnetic head does not crash and the durability of the medium is improved. In the present invention, it is not excluded that a groove extending in the circumferential direction is provided on the surface of the substrate for so-called texturing processing. Further, since it is not necessary to put an anode having magnets radially installed in the plating bath, it is possible to increase the number of sheets to be processed per plating tank, and thus mass production is possible.

[0011]

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a perpendicular magnetic recording medium 20 according to an embodiment of the present invention, and FIG. 2 is a schematic view showing the orientation of the easy magnetic axis of the soft magnetic layer. The substrate 21 is, for example, an aluminum substrate having a thickness of 1.2 mm.
A soft magnetic layer 22 is formed on the top surface. The soft magnetic layer 22 is, for example, a permalloy layer having a thickness of 7 μm, and the magnetic layer 23 as a perpendicular magnetization film is formed on the soft magnetic layer 2. The magnetic layer 23 has a thickness of, for example, 1000 Å and is made of CoCrTa.
It is an alloy layer. Usually, a protective layer (not shown) is provided on this magnetic layer. The surface of the substrate 21 is subjected to a texturing treatment including grooves extending in the circumferential direction. As the substrate material, aluminum, aluminum alloy, glass or the like can be used. In addition to the above-mentioned permalloy, an amorphous alloy can be used for the soft magnetic layer 22, and the permalloy contains 70 to 90% by weight of N.
It is preferable to use an Fe-Ni alloy containing i. Those in this composition range are preferable in terms of magnetic properties.

Thus, in the soft magnetic layer 22, the easy axis 24 of magnetization is oriented so as to extend in the radial direction from the center of the medium.

Next, a method of manufacturing the perpendicular magnetic recording medium having the above structure will be described. FIG. 3 is a perspective view showing a plating bath 31 used when the permalloy layer of the soft magnetic layer is formed by plating. The plating tank 31 is made of vinyl chloride, and a pair of anodes 32, which are magnetized by applying a magnetic field corresponding to the radial direction of the substrate, are installed therein with the surface thereof being vertical. Cathode 3
A substrate support rod 35 extends from the substrate 4, and the substrate 21 of the material to be plated is attached to the substrate support rod 35 with its surface vertical. At the time of plating, the substrate 21 and the Ni anode 32 are installed so as to face each other. Substrate 21 is support rod 3
It is adapted to be rotationally driven via 5.

Before installing the Ni anode 32 and the cathode 34 in the plating bath as shown in FIG. 4, the Ni anode 3
2 is left for a predetermined time on a rod-shaped magnet 41 radially fixed to a fixing jig 42 to magnetize it. The time required for the magnetization depends on the strength of the magnetic field of the magnet, but it is sufficient to perform the magnetization for 1 hour with the strength of the magnetic field of about 40 Gauss. The rod-shaped magnet 41 has an S
The poles are arranged so that the N pole is on the peripheral side. The number of the magnets is preferably 15, for example. Further, when other metal plating is performed, if the anode is a ferromagnetic material, it can be magnetized by the same method. In addition to Ni, for example, F
Rare earth metals such as iron group Gd, Tb, Dy, Ho, Er and Tm such as e and Co may be used.

With the plating apparatus configured in this way,
When the soft magnetic layer 22 such as permalloy is formed on the surface of the substrate by plating, the easy magnetization axis 24 is radially extended and oriented in the soft magnetic layer 22, as shown in FIG.

The plating process may be performed in the same manner as a normal electroplating process. That is, first, the substrate 21 is degreased with an alkali, activated with an acid, washed with an acid, and then treated with a zincate. Next, the substrate 21 is placed in the plating bath 31 as described above, and while the substrate 21 is rotated, permalloy is deposited on the surface by plating. Then, the substrate 21 on which the soft magnetic layer 22 is formed is washed with water.

After that, a magnetic layer 23 as a perpendicular magnetization film is formed by a method such as ordinary sputtering, and a protective film is further formed. Thereby, the perpendicular magnetic recording medium 20 is manufactured.

In the perpendicular magnetic recording medium 20 manufactured as described above, since the easy magnetization axis 24 of the soft magnetic layer 22 is oriented in the radial direction of the medium, the magnetic field moving relatively in the circumferential direction of the medium. When recording / reproducing with the head, the magnetic permeability of the magnetic field does not fluctuate, and a high-level reproducing signal can be obtained constantly. Further, even if an external magnetic field in the vertical direction is applied to the medium, it is possible to prevent the reproduction signal from decreasing. Since no radial groove is provided on the substrate 21, inconveniences such as a magnetic head crash can be avoided.

Next, the results of actually manufacturing a perpendicular magnetic recording medium by the method of this embodiment and testing its characteristics will be described. First, as a substrate to be plated, an aluminum substrate having a diameter of 3.5 inches and a thickness of 1.2 mm was prepared, and the above-described series of plating treatments were performed on the aluminum substrate. Plated under the conditions.

[0021]

[Table 1]

[0022]

[Table 2]

As Example 1, an anode magnetized in advance with a magnetic field before plating was used, and after one hour, a plating treatment was performed in the plating bath 1 hour later, Example 2
As the anode, which was previously magnetized with a magnetic field before plating, was subjected to a plating treatment in the plating bath 7 days after being magnetized. The thing which gave the plating process in the plating bath was produced. The thickness of each permalloy layer is 10 μm. The magnetizing of the anode was carried out by arranging 15 bar magnets radially so that the applied magnetic field to the anode was 30 gauss and left for 1 hour.

Then, the surface of the permalloy layer is subjected to surface roughness 10
A mechanochemical polishing treatment of 0 Å or less was performed, and the surface roughness Rmax was 200 Å or less. As a result, the thickness of the permalloy layer became 7 μm. Its coercive force is 0.8OOe
And the saturation magnetization Bs was 10,000 Gauss.

Then, on the permalloy soft magnetic layer,
A CoCrTa layer as a magnetic layer was provided with a thickness of 1000Å, and a carbon protective film was provided with a thickness of 300Å. The magnetic layer and the protective film were formed by sputtering. Permeance in the circumferential direction and radial direction and reproduction output of 1 MHz when an external magnetic field was applied from the vertical direction were measured for the media of these Examples and Comparative Examples using a certifier (evaluation device). The specifications of the magnetic head used are as shown in Table 3 below. As a result, the permeance ratios in the circumferential direction and the radial direction are as shown in Table 4 below.

[0026]

[Table 3]

[0027]

[Table 4]

FIG. 5 shows the output ratio R to the reproduction output when the external magnetic field is not applied from the measurement result of the reproduction output of 1 MHz. As a result, the permeance ratios of Example 1 and Example 2 were 1.86 to 4.63, and it was found that the easy axis of magnetization was oriented in the radial direction. From FIG. 5, the output ratio R is lowered due to the influence of the external magnetic field in the case of the comparative example in which the easy axis of magnetization is not oriented in the radial direction, whereas in the case of the present embodiment, the external magnetic field is reduced. It can be seen that it is hard to be affected by.

[0029]

In the perpendicular magnetic recording medium obtained by the manufacturing method of the present invention, the easy axis of magnetization of the soft magnetic layer is oriented in the radial direction of the medium without forming a groove in the substrate.
It is possible to keep the magnetic permeability of the soft magnetic layer high at the time of recording / reproducing with the magnetic head and to avoid the fluctuation thereof. Therefore, it is possible to prevent the output of the reproduction signal from decreasing and fluctuating, and it is possible to suppress the influence of the external magnetic field. In addition, since there is no radial groove on the substrate, it is possible to prevent inconvenience such as crash of the magnetic head. Further, according to this method, since it is not necessary to directly insert a bar magnet or the like into the plating bath to apply a magnetic field, it is possible to increase the number of sheets to be processed per bath, and thus the mass production effect is large and it is suitable for industrial production.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram showing the easy axis of magnetization.

FIG. 3 is a perspective view showing a plating apparatus used in the method of the present embodiment.

FIG. 4 is a plan view showing a method of similarly applying anode magnetization before plating.

FIG. 5 is a graph showing an effect of the present invention and an effect of an external magnetic field.

FIG. 6 is a schematic view showing the principle of the perpendicular magnetic recording technology.

FIG. 7 is a schematic view showing an easy axis of magnetization of a conventional medium.

FIG. 8 is a schematic diagram showing an easy magnetization axis of a conventional medium.

FIG. 9 is a plan view showing a substrate surface of a conventional medium.

[Explanation of symbols]

 20; Perpendicular magnetic recording medium 21; Substrate 22; Soft magnetic layer 23; Magnetic layer 24; Easy axis of magnetization 31; Plating bath 32; Anode 34; Cathode 35; Permanent magnet 41; Magnet 42; Fixing jig

Claims (1)

[Claims] 1. A disk-shaped substrate is immersed in a plating bath using an anode magnetized by applying a magnetic field corresponding to the radial direction of the substrate in advance, and a soft magnetic layer is formed on the surface of the substrate. A perpendicular magnetic recording medium comprising: a step of plating to form a soft magnetic layer whose easy axis of magnetization is oriented in a radial direction of a substrate; and a step of forming a perpendicular magnetic layer on the soft magnetic layer. Production method.