JPS6052918A - Magnetic memory medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic memory medium which excels in the high density record/reproduction and the S/N of a servo signal by forming the lower servo oxide magnetic and nonmagnetic layers and an upper data oxide magnetic layer on the surface of a nonmagnetic substrate. CONSTITUTION:A servo oxide magnetic layer 2 consisting mainly of gamma-Fe2O2 containing Co with the coercive force set preferably at 1,000-2,000 Oe is formed on the surface of a nonmagnetic substrate 1 made of glass, an Al alloy coated with an Ni-P alloy, etc. A nonmagnetic layer 3 of SiO2, AlO3, etc. is formed on the layer 2 with 0.2-0.8mu thickness. Then a thin film consisting mainly of Fe3O4 containing Co is provided on the layer 3. Then a heat treatment is carried out in the air to obtain an oxide magnetic layer 4 consisting mainly of gamma-Fe2O3 with the coercive force set preferably at 500-1,000 Oe. The data signals can be recorded to the layer 4 with high density. While the servo signals are recorded to the layer 2. Thus it is possible to obtain a magnetic recording medium which has a high SNR, high durability, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic storage medium such as a magnetic disk used in a magnetic storage device.

Improving the recording density in magnetic storage devices is a constant trend in this industry), and in order to achieve this, it is essential to make the magnetic recording medium thinner.

Conventionally, so-called coating media, in which a mixture of iron oxide fine particles and a binder is coated on a substrate, have been widely used as magnetic disks. As recording density increases, coating media are becoming thinner, but it is extremely difficult to reduce the thickness to several thousand or less and to achieve uniform recording and reproducing characteristics.

Therefore, continuous thin film media, which can be easily made thin, are attracting attention as high-performance magnetic recording media to replace coating media. Co-N prepared by plating method as continuous thin film medium
Although i-P plating magnetic recording bodies have been developed, oxide magnetic thin films, which can be made thin in the same way, are superior in terms of magnetic properties, corrosion resistance, mechanical strength, and the like.

In this way, the recording density of magnetic disk devices has improved year by year,
The linear density of the current equipment is approximately 14,000 FR.
The highest PI and track density are those with a rack pitch of 1100 TPI (23.5 pm). Conventionally, the servo system for data heads that records and reproduces information on the tracks of a disk has generally been a servo surface servo system that uses a disk on which servo signals are recorded, separate from the disk on which data is recorded. In this method, the track positioning accuracy of the magnetic head cannot be increased by the difference in thermal expansion caused by the temperature difference between the disks, so there is a limit to the improvement in track density.

In recent years, unlike the servo surface servo method, γ-Fe s O
Experimental results have been reported on a data surface servo method (buried servo method) in which two magnetic layers, upper and lower, are used in a coated disk using S particles, with servo information recorded in the lower layer and data information recorded in the upper layer.

However, since it is difficult to reduce the magnetic film thickness in γ-Fe,0 coating disks (0,
It is difficult to significantly increase the recording density (the limit is said to be 5 μm), and furthermore, the signal-to-noise ratio (SNR) during high-density recording and reproduction is low.

The purpose of the present invention is to improve these problems and provide a magnetic memory body that is capable of high-density recording and has a good SNR and is suitable for a data surface servo system.The basic structure thereof uses a sputtering method. The use of a continuous oxide thin film for the upper data magnetic thin film and the lower servo magnetic film through a non-magnetic layer in the double-layer magnetic storage material made it extremely excellent as a magnetic storage material for secondary read servo. It has certain characteristics.

That is, according to the present invention, a nonmagnetic substrate, a lower oxide magnetic layer covering this substrate, a nonmagnetic layer covering this oxide magnetic layer, and an upper oxide magnetic layer covering this nonmagnetic layer are provided. A magnetic storage body is provided, characterized in that it includes:

Suitable non-magnetic substrates include glass, alumite-coated aluminum alloys, or nickel-phosphorus alloy-coated aluminum alloys whose surfaces have been polished, and the lower oxide magnetic layer covering this is γ- containing additives such as Co. Fe
s Om as the main component, or r-Fe2O2 and Fe, 0. An iron oxide magnetic layer containing an intermediate composition as a main component is suitable, and as a non-magnetic layer containing this, S io, ,
Al*o, , a-Fe, O, etc. have a thickness of 0.
2 to 0.8 μm is preferable. The upper oxide magnetic layer covering this is γ-Fe*0 containing additives such as Co.

or γ-Fe, 0. An iron oxide magnetic layer mainly composed of an intermediate composition of Fe,04 and Fe,04 is suitable. Servo signals are recorded in the lower oxide magnetic layer and data signals are recorded in the upper iron oxide magnetic layer. The lower oxide magnetic layer has a thickness of 100% so that there is no influence of the head magnetic field when data signals are recorded on the upper oxide magnetic layer.
A coercive force of 0 to 20,000 e is preferable, while a coercive force of 500 to 10,000 e is preferable for the upper oxide magnetic layer because data signals can be easily written and recorded at high density. Since the SNR of the signal is improved, a good data plane servo system for SNH can be realized.

The features of the magnetic storage body according to the present invention will be explained below using examples.

Example The structure of the magnetic storage body of this example is shown in the figure. As the non-magnetic substrate 1, an aluminum alloy substrate coated with alumite and mirror-polished was used, and on this was F containing 2.0% to 40% by weight of cobalt and 2g6 of copper.
The sputtering pressure was 4X 10-'Torr in an argon atmosphere using e, O, as a target.

Film thickness from 0.2μm to 05μ with sputtering power 2.0KW
An iron oxide magnetic thin film containing Fe*04 as a main component was formed, and this was oxidized in the atmosphere at 300° C. for 1 hour to obtain a lower oxide magnetic layer 2. This was an iron oxide magnetic thin film whose main component was γ-Fe, 0, up to a film thickness of approximately 0 and 25 μm;
The coercivity of these magnetic films ranges from 100"0-Oe to 20" 0-Oe.
It was 000e.

Next, a 5-inch nonmagnetic layer 3 is formed on the lower oxide magnetic layer 2.
s with a thickness of 0.2 μm to 0.8 μm, and on top of this, 13% to 20% by weight of cobalt and 29% of copper.
Using a Fe104 target containing 0.6 to 100% F, a film thickness of 0.1 pm to 0.2 pm was formed in an argon atmosphere at a sputtering pressure of 4 x 10-' Torr and a sputtering power of 1.75 KIV.
Forming an iron oxide magnetic thin film mainly composed of e s Oa,
This was oxidized in the air at 275°C for 1 hour to produce γ-FesOs.
An upper oxide magnetic layer 4 containing as a main component was formed.

Upper oxide magnetic layer 4 of the magnetic recording body thus obtained
The recording density of the data signal recorded in I)s is when the gap length of the magnetic head is 0.15 μm to 1.0 μm.

(Recording density of reproduction output that is 1/2 of solitary wave output) is 2
High density characteristics with good SNR were obtained with 5 to 66 KFRP I. In addition, the SNR of the servo signal recorded in the lower oxide magnetic layer 2 was improved by 4 to 5 dB compared to the Co-N i-P plated magnetic medium because the lower oxide magnetic layer 2 is a high coercive force magnetic layer. .

As shown in the examples above, when realizing the lateral servo system on a magnetic double layer disk, the upper and lower magnetic layers are made of γ-Fe doped with cobalt, 0. By using a magnetic medium produced by sputtering, it has become possible to increase the density of the data signal and increase the SNR of the servo signal.

[Brief explanation of the drawing]

The figure is a cross-sectional view of a magnetic memory used in an example of the present invention. 1 is a nonmagnetic substrate, 2 is a lower oxide magnetic layer for recording servo signals, 3 is a nonmagnetic layer, and 4 is an upper oxide magnetic layer for recording data signals.

Claims (2)

[Claims] (1) Includes a non-magnetic substrate, a lower oxide magnetic layer covering this substrate, a non-magnetic layer covering this oxide magnetic layer, and an upper oxide magnetic layer covering this non-magnetic layer. Characteristic magnetic memory. (2) The coercive force of the lower oxide magnetic layer of the magnetic memory is 100
2. A magnetic storage body according to claim 1, wherein the coercive force of the upper oxide magnetic layer is between 500 and 1000 Oe.