JPS58189349A - Co alloy for magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled alloy undergoing a remarkably slight reduction of the saturation magnetizability with the passage of time, by adding restricted amounts of Y, Zr and Ti to a Co-Cr alloy having a specified composition. CONSTITUTION:This Co alloy consists of, by weight, 9.0-22.5% Cr, 0.001-0.10% Y, 0.1-2.0% Zr and/or 0.1-0.2% Ti, and the balance Co or further contains 0.1-2.0% Al. Y inhibits the reduction of the saturation magnetizability with the passage of time. Zr and Ti prevent the deterioration of the saturation magnetizability with the passage of time in the presence of Y. The deterioration of the saturation magnetizability with the passage of time is further inhibited by adding Al.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic recording medium that exhibits very little decline in magnetic properties, especially saturation magnetization, over time when used as a magnetic recording medium.
It concerns base alloys.

Conventionally, magnetic disks, floppy disks, audio magnetic tapes, VTR magnetic tapes, magnetic photographic disks, computer magnetic tapes, etc., have been manufactured by using magnetic tape on the surface of a substrate such as a plastic film or metal sheet.
Using surface treatment techniques such as sputtering method, vacuum evaporation method, and chemical plating method, for example, Cr: 9.0 to 22
．． It is well known that a magnetic recording medium is manufactured by forming a thin film of a Co--Cr alloy having a composition of 5% by weight and the remainder consisting of Co and unavoidable impurities. This Co-Cr alloy magnetic recording medium is
Because it has large magnetic anisotropy and saturation magnetization, it is easy to maintain the signal level even when the film is made thin, and it has been put into practical use, especially for perpendicularly magnetized films.

However, in the above-mentioned Co-Cr alloy magnetic recording medium, there is a problem that the initial saturation magnetization gradually decreases over time, which results in a decrease in the recording/reproducing signal level in magnetic recording and reliability. It was a detriment to sexuality. Note that this decrease in the saturation magnetization of the magnetic recording medium over time is thought to be caused by the formation of oxides due to atmospheric oxidation.

Therefore, from the above-mentioned viewpoint, the present inventors have developed the above-mentioned C, which has been conventionally used as a magnetic recording medium.

-Cr alloy, that is, a Co-Cr alloy containing 9.0 to 225% by weight of Cr, with the remainder consisting of Co and unavoidable impurities. As a result of conducting research from a material perspective in order to resolve the temporal decline in saturation magnetization that occurs when a -Cr alloy is used as a magnetic recording medium, we found that this Co-Cr alloy contains Y: 0.001-0.10 as an alloy component. Chi and
Zr: O, 1-2.0% and Ti: 0.1-2
．． When one or two of 0% is contained, the resulting Co-based alloy exhibits significantly less decrease in saturation magnetization over time when used as a magnetic recording medium. They obtained the knowledge that the decrease in saturation magnetization over time can be further suppressed.

Therefore, the present invention has been made based on the above findings, and a Co-based alloy for magnetic recording media is prepared such that, in weight percent, Cr: 9.0-22.5%, Y: 0.001-0.
10%, and one or two of Zr: 0.1 to 2.0% and T'i: 0.1 to 2.0%, and if necessary, Al! :0.1~2.0%
It is characterized by a composition in which the remainder consists of CO and unavoidable impurities.

Next, the reason why the composition range of the Co-based alloy of the present invention is limited as described above will be explained.

(a) Cr The Cr component has a saturation magnetization of 80 to 850, which is the practical range.
It has the effect of adjusting to Gauss, but if its content is less than 90 Gauss, the saturation magnetization will exceed 850 Gauss and become too high.
As a result 1, for example, when used as a perpendicular magnetization film, it is impossible to achieve magnetization orientation perpendicular to the film surface.On the other hand, if the content exceeds 225%, only a saturation magnetization of less than 80 Gauss can be obtained, and as a result, the reproduction output is If the S/N ratio deteriorates, making it unusable, the content was reduced to 9.0.
It was set at ~22.5%.

(b) Y The Y component has the effect of suppressing the decrease in saturation magnetization over time as described above, but if its content is less than O,OOl, the desired effect cannot be obtained; If the Cr content exceeds 10%, not only will the above action tend to deteriorate again, but if the Cr content is relatively high, it will no longer be possible to secure a practical saturation magnetization of 80 Gauss or more. Therefore, the content is O,OO1~0.
It was set at 10%.

(c) Zr and T1 These components have the effect of preventing the deterioration of saturation magnetization over time when coexisting with Y, but if their content is less than 0.1% each, the desired effect cannot be obtained. On the other hand, if the Cr content exceeds 20 Cr, not only does the above-mentioned effect tend to deteriorate again, but also a practical saturation magnetization of 80 Gauss or more cannot be obtained in the case of a high Cr content.

The content was determined to be 01 to 2.0%, respectively.

(d) AQ Furthermore, when M is included, the deterioration of saturation magnetization over time is suppressed, so it is included as necessary, but if the content is less than 0.1%, the desired suppressing effect cannot be obtained. On the other hand, if the content exceeds 2.0%, it will be difficult to secure a practical saturation magnetization of 80 Gauss when the Cr content is relatively high, so the content should be reduced to 0.1%.
It was set at ~2.0%.

Next, the Co-based alloy of the present invention will be specifically explained with reference to Examples.

Examples Co-based alloys 1-18 of the present invention and Comparative C, each having the composition shown in Table 1, were prepared by a conventional melting and casting method.
Ingots of O-base alloys 1 to 4 were each prepared, and then from these ingots diameter: 125 mmφ x thickness: 1.51. A spuntering night case with the dimensions of
RF (radio frequency) sputtering was performed under the conditions of atmospheric pressure 2XlOtorr to produce a magnetic recording medium with a thickness of 202 μm having substantially the same composition as the alloy composition on the surface of a polyester film substrate with a thickness of near μm. A thin film was formed. In addition, the above-mentioned Comparative Co-based alloys 1 to 4 all have compositions in which the content of one of the constituent components (indicated with a * mark in Table 1) is outside the scope of the present invention. It is something.

Next, regarding the various magnetic tapes obtained as a result,
Immediately after production, the saturation magnetization was measured after being left in a constant temperature and humidity chamber at a temperature of 60° C. and a humidity of 90% for 7 days, 30 days, and 100 days, and the rate of decrease was calculated. These results are also shown in Table 1. Note that the saturation magnetization was measured using a vibrating sample type magnetic measurement device with 5 applied magnetic fields: 13 KO
It was measured under the conditions of e.

From the results shown in Table 1, it can be seen that in the magnetic tapes in which the magnetic recording medium is composed of the CO-based alloys 1 to 18 of the present invention, the decrease in saturation magnetization over time is extremely small.
80 to 850 maintains the practical saturation magnetization of the magnetic tape for a long period of time, whereas magnetic tape using Comparative CO-based alloy 1, which does not contain Y, Zr, and T1 as a magnetic recording medium (conventional magnetic tape Comparative Co-based alloys 2. and 2. corresponding) show a very significant decrease in saturation magnetization over time, while comparative Co-based alloys 2. and 2. All of the magnetic tapes using 3.4 exhibited a saturation magnetization of less than 80 Gauss, and it is clear that they cannot be put to practical use.

As mentioned above, according to the CO-based alloy of the present invention.

When this is used as a magnetic recording medium, the saturation magnetization decreases over time very little, so recording in magnetic recording and
This allows the reproduction signal level to be maintained at a high level at all times.

Applicant: Mitsubishi Metals Corporation Agent Tomi 1) Kazuo

Claims (2)

[Claims] (1) Cr: 9, O ~ 22.5%, Y: O, OO1
~0.10% and Zr:O, 1~20%
and T1: 01 to 2.0%, and the remainder has a composition consisting of cobalt and unavoidable impurities (weight%), and when used as a magnetic recording medium, it is magnetic. Co-based alloy with very little deterioration of properties over time. (2) Cr: 9.0-22.5%, Y: O, O
Contains Ol ~ 010, and Zr: 0.1~2
．． 0% and T1: 0.1 to 2.0%, and further I/i: AE: 0.1 to 2.0%.
A Co-based alloy having a composition (by weight) with the remainder consisting of CO and unavoidable impurities, and which exhibits extremely little deterioration of magnetic properties over time when used as a magnetic recording medium.