JPH0322646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a perpendicular magnetic recording medium capable of high-density recording.

(Prior Art) A so-called two-layer media type perpendicular magnetic recording body in which a soft magnetic film and a perpendicular magnetic film are sequentially laminated on a non-magnetic base material surface is known.

(Problems to be Solved by the Invention) In the perpendicular magnetic recording medium of the above type, the interaction between the soft magnetic film and the recording/reproducing head is particularly strong during reproduction, and especially during reproduction, the reproduction output is caused by the soft magnetic film. It is small in the direction of easy magnetization of the film and large in the direction of difficult magnetization. This is because the initial magnetic permeability of the soft magnetic film is small in the direction of easy magnetization and large in the direction of difficult magnetization. Therefore, for example, in the case of a disk-shaped perpendicular magnetic recording medium, when magnetic anisotropy occurs in the soft magnetic film, the initial magnetic permeability changes in the circumferential direction, that is, in the direction of movement of the head. Modulation will occur. In general, the magnetic anisotropy of a soft magnetic film is caused by various conditions at the time of production.
When running a tray and applying a soft magnetic film to it by sputtering, depending on the sputtering conditions,
Magnetic anisotropy occurs parallel to the running direction,
Magnetic anisotropy may occur in the direction perpendicular to the running direction, and as a result, the resulting magnetic recording disk product has a problem of large modulation during reproduction.

(Means for Solving the Problems) The present invention provides a perpendicular magnetic recording medium that solves the above problems and can reproduce at a stable high output without modulation by controlling the magnetic anisotropy to a constant level. In a perpendicular magnetic recording body in which a soft magnetic film and a perpendicular magnetic film are successively laminated on the surface of a non-magnetic base material, there is a magnetic field perpendicular to the direction in which the head moves during recording and reproduction on the surface of the non-magnetic base material. It is provided with countless fine unevenness lines extending in the direction of.

(Example) Next, examples of the present invention will be described.

The non-magnetic base material is made of a non-magnetic material such as aluminum or a synthetic resin material, and is the same as that conventionally used, and its shape is a disc shape, a tape shape, etc. On the surface of such non-magnetic base material, by appropriate means,
Countless fine unevenness lines are formed perpendicular to the recording/reproducing direction. FIG. 1A shows a disc-shaped non-magnetic base material, a so-called disk substrate 1, in which countless grooves 2 are formed in a direction perpendicular to the recording/reproducing direction X indicated by the arrow, in other words, in the radial direction of the disk. and the first
Figure B shows a tape-shaped non-magnetic base material, a so-called tape substrate 1, on which countless parallel grooves 2 are formed in a direction perpendicular to the recording and reproducing direction shown by the arrow, in other words, in the width direction of the tape. show. The depth of the groove 2 is
Approximately 1000 to 10 Å is good. In the case of disk substrates, mirror finishing is generally performed after forming a soft film such as NiP plating, but the grooves are carved either before or after the mirror finishing. can be done.

The formation of the grooves can be achieved, for example, by making scratches with sandpaper of about 6000 grit, or by buffing using a liquid in which a relatively coarse abrasive is suspended. The so-called two-layer film medium type perpendicular magnetic recording body of the present invention can be obtained by processing the base material a having a countless number of uneven striped surfaces, produced in this manner, using a conventional method using, for example, a conventional in-line sputtering device. FIG. 3 shows an in-line sputtering device 4 in its manufacturing process, with reference numeral 5 to its preparation chamber, 6 to the sputtering chamber, 7 to the unloading chamber, 8 to the sputtering cathode for forming a soft magnetic film, and 9 to the perpendicular magnetic Sputter cathode for film formation, 10 is a tray, 11
12 is a vacuum exhaust port connected to the partition chamber 5, the sputtering chamber 6 and the take-out chamber 7 through a control valve, respectively;
1 shows a partition with on-off valves provided between the chambers 5, 6, and 7 and at both outer ends thereof. Thus, in order to sequentially laminate the soft magnetic film and the perpendicularly magnetized film on the substrate a of the disk having the uneven stripes shown in FIG. , and sputter a soft magnetic material and a ferromagnetic material in the sputtering chamber 6 by moving in the direction of the arrow. A perpendicular magnetic disk of the present invention having a magnetic film 1b is obtained.

Next, an experimental example will be explained.

20 μm of NiP amorphous layer is placed on the top surface of the hollow disc-shaped Al plate.
The disk substrate is plated to a thickness of m,
The surface of this substrate is immersed in water in which alumina abrasive is suspended, and then polished radially from the center of the substrate using a buffing cloth to form countless fine grooves extending radially. accomplished.

The depth of the groove at this time was approximately 200 Å. The substrate having the grooves created in this way is placed in an in-line sputtering device shown in Figure 3, and a soft magnetic film made of Mo-permalloy with a thickness of 0.5 μm and a Co-permalloy with a thickness of 0.2 μm are placed on the surface with the grooves. A perpendicular magnetic film made of 20 at % Cr was sequentially formed by sputtering and removed to produce a two-layer medium type perpendicular magnetic recording disk of the present invention. On the other hand, for comparison, the same two-layer film medium made of the same material and having the same thickness was immediately charged into an in-line sputtering machine without performing the concave groove forming process and sputtered under the same conditions as above. A type of perpendicular magnetic recording disk was manufactured.

Recording and reproduction were performed on both of these disk products at a recording density of 1 KBPI using a main pole excitation type vertical head, and the reproduction envelope was measured. In addition, the initial magnetic permeability measured in the circumferential direction of both was determined.
The results are shown in FIGS. 4 and 5. In the figure, θ
The position on the horizontal line in the direction corresponding to the tray movement direction is set to 0°, and this is used as the base line to represent the angular position on the circumference where the head travels from now on.After one rotation, the position on the horizontal line is set to 360° again. This is what I did. In each figure, I shows the characteristic curve of the disk of the present invention, and C shows the characteristic curve of the conventional disk.

From these graphs, it can be seen that the conventional disk without grooves on the substrate has extremely large fluctuations in both reproduction output and initial permeability and is wavy, whereas the disk of the present invention with grooves on the substrate in a predetermined direction has a reproduction output It is recognized that both the initial magnetic permeability and the initial magnetic permeability are stable with almost no fluctuation, and the reproduction output is large as a whole.

In this way, according to the present invention, on the base material surface,
Since we created a perpendicular magnetic recording body in which a soft magnetic film and a perpendicular magnetic film were sequentially laminated on a material on which fine uneven stripes were formed perpendicular to the running direction, the magnetic anisotropy could be adjusted parallel to the direction in which the uneven stripes were formed. Because the magnetic anisotropy can be generated, the magnetic anisotropy can be controlled to a constant level, and during recording and reproduction, the head travel direction is always in the direction of difficulty in magnetization, the initial magnetic permeability is high, and there is almost no modulation. This provides the effect of obtaining stable and high playback output.

[Brief explanation of drawings]

1A and 1B are plan views of a base material of a perpendicular magnetic recording medium according to an embodiment of the present invention, FIG. 2 is a partially cutaway plan view of an embodiment of the present invention, and FIG. The figure is a partially cutaway side view of an example of an apparatus for manufacturing the product of the present invention, FIG. 4 is a diagram showing reproduction output characteristics comparing the product of the present invention and a conventional product, and FIG. is a diagram showing similar initial permeability characteristics. DESCRIPTION OF SYMBOLS 1... Non-magnetic base material, 2... Recessed stripes, a... Base material with uneven stripes, 1a... Soft magnetic film, 1b... Perpendicular magnetic film, 4... Sputtering device, I... of the present invention Reproduction output, initial permeability.

Claims (1)

[Claims] 1. In a perpendicular magnetic recording body formed by successively laminating a soft magnetic film and a perpendicular magnetic film on the surface of a non-magnetic base material, a head is placed on the surface of the non-magnetic base material during recording and reproduction. A perpendicular magnetic recording medium consisting of countless fine concave and convex stripes extending in a direction perpendicular to the direction of movement. 2. The perpendicular magnetic recording body according to claim 1, wherein the depth of the uneven stripes is about 1000 to 10 Å.