Perpendicular magnetic recording medium and method for manufacturing same

Abstract

A perpendicular magnetic recording medium is disclosed in which each magnetic crystal grain in the magnetic recording layer has a multilayer structure and has a configuration like a truncated cone shape, in which the crystal grain of the final layer deposited in the film surface side at the final stage is smaller than the diameter of the crystal grain in the initial layer deposited on the substrate side at the initial stage. The invention improves S / N (signal output to noise ratio) by enhancing signal output and reducing noises. The medium is produced by a simple manufacturing method suitable for mass production, and provides a medium of high recording density by improving recording resolution.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority from Japanese application Serial No. JP PA 2004-010427, filed on Jan. 23, 2004, the contents of which are incorporated herein in their entirety. BACKGROUND OF THE INVENTION [0002] A. Field of the Invention [0003] The invention relates generally to a perpendicular magnetic recording medium mounted on various magnetic recording apparatuses and a method for manufacturing such a medium. [0004] B. Description of the Related Art [0005] In technologies for achieving high density magnetic recording, perpendicular magnetic recording is drawing attention as a substitute for conventional longitudinal magnetic recording. [0006] Alloy materials of CoCrPt, CoCrTa, and the like have been used for a magnetic recording layer material of a perpendicular magnetic recording medium employing perpendicular magnetic recording. In these alloy materials, the nonmagnetic substance chromium segregates into a grain boundary and mag...

AI Technical Summary

Benefits of technology

"The present invention provides a perpendicular magnetic recording medium and a manufacturing method that reduces noise and enhances the signal-to-noise ratio. The medium includes a magnetic recording layer with a plurality of magnetic crystal grains that have a multilayer structure with increasing saturation magnetization towards the final layer in the film surface side. The method includes separate film deposition steps with varying conditions, resulting in a plurality of magnetic crystal grains each with a multilayer structure. The magnetic crystal grains have a truncated cone shape with a smaller diameter in the final layer, enhancing signal output and reducing noises. The medium and method provide high-density recording and improved performance for perpendicular magnetic recording."

Problems solved by technology

In a perpendicular magnetic recording medium, however, the heating or substrate bias voltage application as conducted in the in-plane medium can segregate only a small amount of chromium, resulting in high media noise.

It has been difficult, however, to promote segregation in the granular magnetic recording layer by a process that is suitable for mass production.

At the same time this means that taking out magnetic flux in high density recording is difficult.

While a medium structure is required that achieves low noise and high signal output even at high recording density, such a medium structure has never been proposed.

There have been various problems in achieving the desired result.

Because deposition of a granular film with substrate heating raises problems of mixing a nonmagnetic phase with an alloy phase and / or oxidation or nitridation of cobalt, the film must be deposited without substrate heating.

However, film deposition without substrate heating cannot achieve sufficient isolation between the alloy phase and the nonmagnetic phase, which raises a problem of insufficient noise reduction.

Heat treatment at such a high temperature and for relatively long time is not suitable for mass production.

It is unfortunately very difficult to obtain a film that is homogeneous over a disk surface using an arrangement that places two targets in equipment for mass production.

Therefore, this technique is not suitable for mass production.

However, none of these techniques is suitable for mass production.

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