JPS60138735A - Heat treatment of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain an excellent recording medium without cracking in a magnetic film by sputtering an Ni-Co alloy target in gaseous Ar contg. N2 or O2 to form a thin Co-Ni film contg. N or O on a non-magnetic substrate then subjecting the film to a heat treatment under specific heating up conditions. CONSTITUTION:A thin Ni-Co alloy film contg. 12-17atom% N or O or N and O is formed on, for example, an anodized Al substrate, Al2O3 ceramic substrate, etc. in an atmosphere of gaseous Ar contg. N2 or O2 or gaseous Ar contg. air by a vacuum sputtering method using an Ni-Co alloy target contg. 35atom% Ni. The substrate on which the thin magnetic film is formed is heated from a room temp. up to a prescribed temp. (400-500 deg.C) at an average heating up temp. of <=20 deg.C/min in a vacuum or air furnace. If the magnetic film is heat- treated in the above-mentioned way, no cracks are generated at all in the magnetic film and the excellent magnetic recording medium having an improved squareness ratio and residual magnetic flux density is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in co-Ni thin demagnetized recording media.

By sputtering a Co-Ni alloy in an Ar and nitrogen mixed atmosphere, a thin film medium is formed on a substrate, and by heat-treating this in a vacuum or the like, a thin film magnetic recording medium with excellent magnetic properties can be produced. Japanese Patent Publication No. 57-72307. and J, A, P, 53, (5) May 1982
．． J, A, P, 53 (10) Oct, 19
82゜J P N , J , A ppl, phys,
Vol. 211982 No. 11, etc.

In particular, in the above patent publication, heat treatment is described at temperatures of 250°C or higher and 700°C.
It is said to be carried out at ℃. Furthermore, in the above paper, the temperature is mainly 290°C.

Now, as pointed out in these papers, cracks with a width of about 300 A called "hollow channels" are formed in the film after heat treatment.

On the other hand, as the linear recording density increases due to the improvement in the magnetic recording density, not only the film thickness of the medium but also a high S/N ratio is required, and a high quality thin film medium is required.
There is a need for thin films that are free of els.

An object of the present invention is to provide a heat treatment method in which the above-mentioned cracks do not occur during heat treatment.

In order to solve this objective, we focused on the start of degassing of nitrogen and oxygen in the film, and investigated various heating rates from room temperature to a predetermined heat treatment temperature.

As a result, 7 mm x 81
111+1X If a 2ml thick sample is inserted and heated rapidly, cracks will occur;
It has been found that when the temperature is raised to the heat treatment 1 temperature of 400° C. to 500° C. at an average heating rate of 1 minute or more, the above-mentioned cracks are not generated. Heating at a rate of 18° C./min or less is more desirable, while cracking was observed at a heating rate of more than 7° C./min. Furthermore, by preventing cracks, improvements in squareness ratio and residual magnetic flux density were also observed.

Examples will be explained in detail below.

EXAMPLE A thin film medium was sputtered onto an anode aluminum aluminum oxide substrate, an AI 20a ceramic substrate, a stainless steel substrate, and a glass substrate using a flat plate magnet 1-ron sputter in an N2 or 02 or air-containing Ar gas atmosphere under the following conditions.

Initial exhaust 1 to 2 x 10 TOrr Total atmospheric pressure 16 mTorr Input power 11 (W) Composition Co -30 atomic% N1 Target diameter 12 h Pole spacing 120 mm Film thickness 1000 A Substrate dimensions 7 x 8 x 2 mm thick Sputtered film created under the above conditions As a result of X-ray diffraction, both exhibited halo pattern diffraction spectra characteristic of amorphous materials, and almost no magnetism appeared before heat treatment.

Heat treatment was performed using a vacuum or air furnace. In each case, 400 samples were used.
The sample was maintained at a predetermined heat treatment temperature of 500°C to 500°C for 1 hour.

Thereafter, the sample was cooled to a humidity of around 30° C. in about 1 hour, and the sample was subjected to magnetic property measurements. The magnetic properties were measured in the horizontal direction of the film using a sample vibrating magnetometer.

The presence or absence of cracks was determined by SE and M observation at io and ooo times.

If the average heating rate from room temperature to a heat treatment temperature of 400°C to 500°C is approximately 0°C/min or more, then the known example J is used.
, AFrill, 1) hys, vol, 53 No.
5 May 1982 paper P, 3736, cracks (so-called bowlchannels) were observed, but when the average heating rate was 20°C/min or less, no cracks were observed, and only a satin-like pattern was observed in both cases. Ta.

There were no major differences in these situations depending on the substrate.

Table 1 shows these results together with the magnetic properties after heat treatment.

/ When there are no cracks, the residual magnetic flux density is 3r and the squareness ratio S (Br /B sea urchin), but 8
3 shows the magnetic flux density in a 3 kOe magnetic field.

The effect of preventing cracks by avoiding rapid heating from room temperature to the heat treatment temperature is obvious, and it is also superior to recording thin film media in terms of magnetic properties.

Note that the films after heat treatment are all crystallized, c and p.

It was confirmed by X-ray diffraction that it has a structure with its C-axis oriented horizontally to the plane.

According to the present invention, Co-N having an easy axis of magnetization in the in-plane direction
The i-alloy sputtered film can be made without cracks and has better magnetic properties as a high-density magnetic recording medium.

Claims (1)

[Claims] A C0-Ni alloy target with a Ni content of 35 at% or less is sputtered in an Ar gas atmosphere containing an appropriate amount of nitrogen, an Ar gas containing an appropriate amount of oxygen, or an Ar gas atmosphere containing an appropriate amount of air, and nitrogen is deposited on a nonmagnetic substrate. Alternatively, when forming a Co-Ni alloy thin film containing 12 to 17 at% of oxygen, nitrogen, and oxygen, and heat-treating the film to obtain magnetic properties suitable for a magnetic recording medium, the film may be heated at a predetermined heat treatment temperature (400°C) from room temperature. 500° C.) at an average temperature increase rate of 20° C./min or less.