JPS6057523A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium having the recording and reproduction equal to the recording and reproduction of cobalt chromium and having excellent durability by using a thin cobalt carbon alloy film having a specific structure as a cobalt alloy constituting a thin cobalt alloy film. CONSTITUTION:Cobalt carbide is formed at the grain boundary of cobalt, by which the same effect as parting of the mutual exchange effect by segregation of chromium is provided and wear resistance is improved by cobalt carbide. A part (a) is a ferromagnetic material using cobalt carbon alloy and (b) is a part using a cobalt chromium alloy and is paramagnetic by which the partition of a mutual exchange effect and the wear resistance of the film are improved. The C-axis of the crystal of Co is required to face the direction perpendicular to the film plane and the film is required to have the high magnetic anisotropy in the vertical direction and moreover the width of the magnetic wall is required to be small in order to form the excellent vertical magnetized medium. The thin cobalt carbon alloy film of this invention has the crystal of cobalt and the structure in which cobalt carbide is precipitated at the grain boundary thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a perpendicular magnetic recording medium.

A perpendicular magnetic recording medium has magnetic anisotropy in a direction perpendicular to the medium surface, and the magnetic moment within a recorded magnetic domain is oriented perpendicular to the medium surface. Conventionally, perpendicular magnetic recording media have mainly been made of cobalt-chromium alloy thin films. In order for a cobalt chromium thin film to be used as a perpendicular magnetic recording medium, it must have magnetic anisotropy perpendicular to the cobalt chromium thin film, and must have a layer in which chromium is segregated at the grain boundaries, and an exchange interaction between each grain. must be weakened to obtain as steep a magnetization reversal as possible. A medium having the above characteristics can be produced relatively easily by forming a cobalt chromium thin film using a sputtering method. However, cobalt chromium thin films have drawbacks in durability. In other words, since the cobalt chromium thin film is susceptible to MflJ, it is easily crushed by the magnetic head, and in severe cases, cracks may occur in the film, and recording and reproducing may become impossible in a short period of time.

Perpendicular magnetic recording technology was originally conceived as high-density recording, and as the recording density increases, the gap between the medium and the head must be further reduced. Therefore, it is desirable that the protective layer or il#7 slipping layer of the medium be as thin as possible. For this reason, cobalt chromium films with poor wear resistance have many problems.

The present invention has been devised to improve this drawback. By forming cobalt carbide at the cobalt grain boundaries, we achieved the same effect as the disruption of exchange interaction due to chromium segregation, and the cobalt carbide improved wear resistance. Figure 1 shows the structure of JIA. (The part (a) in the figure is cobal) The IJ notch 4r is paramagnetic, which disrupts exchange interactions and improves the wear resistance of the film.

In order to be an excellent perpendicularly magnetized medium, it is necessary that the C axis of the CO crystal (hexagonal close-packed) is oriented perpendicular to the film surface and that it has high magnetic anisotropy in the perpendicular direction. But that alone is not enough. Furthermore, when the distributed magnetic domains are formed, the magnetization reversal is required to be steep, that is, the a-wall is required to be narrow. Exchange energy and anisotropy energy are generally the factors that determine the magnetic domain wall density, but if a paramagnetic layer is provided at the grain boundary, the exchange interaction can be blocked and the magnetization reversal region can be significantly reduced. can.

Next, examples will be shown.

The conversion method used reactive sputtering. A cobalt-carbon alloy fXv film was created by attaching a cobalt target to a magnetron type sputtering device and sputtering by introducing a mixed gas of argon and methane gas. Pyrex glass is used for the substrate.

Figure aS2 shows the X-ray diffraction of the sputtered film.

FIG. 5 shows an X-ray dispersion curve. In addition, the 41st graph shows a magnetization history curve obtained by a vibrating sample magnetometer. From the X-ray diffraction in FIG. 2, it can be seen that there is only a peak from the 002 plane of the hexagonal crystal, indicating C-axis orientation. Also, it can be seen from the magnetization history curve in Figure &'S4 that it is a perpendicularly magnetized film.

Permalloy on plastic film and this product [
A magnetic recording disk having a two-layer TIG structure of a di-J cobalt-carbon alloy thin film was prepared, and recording/reproducing characteristics and durability tests were conducted. FIG. 5 shows the recording density characteristics. The disk used in the test had a diameter of 5 inches, and the head used was a single-pole type perpendicular magnetic head with a thickness of 0.5 μm. The recording density characteristics of a disk using a cobalt chromium alloy thin film are shown by a broken line, and they have almost the same characteristics. Durability was compared between a medium using cobalt chromium and a disk using the above-mentioned cobalt carbon alloy.

In the test, the disk was continuously rotated at a speed of 5 rps, and changes in head output were examined.

Figure 6 shows the results. Compared to cobalt chromium, cobalt carbon is extremely durable.

As described above, a perpendicular magnetic recording medium using a cobalt-carbon alloy thin film has recording and reproducing characteristics equivalent to those of cobalt-chromium, and is extremely durable.

[Brief explanation of the drawing]

FIG. 1 shows the structure of the cobalt carbon film of the present invention. (a) is a cobalt crystal grain. (mouth) is a layer of cobalt carbide. (c) is the substrate. Figure 2 shows the X-ray diffraction spectrum of the cobalt carbon film. FIG. 6 shows the same X-ray dispersion curve. Figure 4 shows the magnetization curve. FIG. 5 shows the relationship between recording density and output using a single-pole magnetic head with a thickness of 0.5 μm. (a) is a medium using a cobalt-carbon alloy, and (b) is a medium using a conventional cobalt-chromium alloy. FIG. 6 shows the durability of the medium used in FIG. 5 due to head running. (A) is a medium using cobalt carbon, and (
) indicates a medium using cobalt chromium. Applicant Suwa Seikosha Co., Ltd. Agent Patent Attorney Mogami Mutsumi Figure 1 Figure 2 Figure 3 '1 Figure 4 Imperial Rescript 4#L Chuko CJ3nJ Figure 5

Claims (2)

[Claims] (1) A perpendicular magnetic recording medium using a cobalt alloy thin film, characterized in that a cobalt-carbon alloy thin film is used as a conochrite alloy constituting the thin film. (2) A perpendicular magnetic recording medium characterized in that the thin film of a cobalt carbon alloy according to claim 1 has a structure in which cobalt carbide is precipitated at the grain boundaries of cobalt crystals.