JPS6056411B2 - Co-based alloy for magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic recording medium that exhibits very little deterioration in magnetic properties, especially saturation magnetization, over time when used as a magnetic recording medium.
This relates to o-based alloys.

Conventionally, magnetic disks, floppy disks, audio magnetic tapes, VTR magnetic tapes, magnetic photographic disks, computer magnetic tapes, etc.
For example, Cr: 9.0 to 2 is applied to the surface of a substrate such as a plastic film or metal sheet using surface treatment techniques such as sputtering, vacuum evaporation, and chemical plating.
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 2.5% by weight and the remainder consisting of Co and unavoidable impurities. Since this Co--Cr alloy magnetic recording medium has large magnetic anisotropy and saturation magnetization, it is easy to maintain a signal level even when the film is made thin, and has been put into practical use, especially for perpendicularly magnetized films. However, the above C
A problem with o-Cr alloy magnetic recording media is that the initial saturation magnetization gradually decreases over time, which results in a decrease in recording and reproduction signal levels in magnetic recording and impairing reliability. It was hot.

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 investigated the above-mentioned Co-
We focused on a Cr alloy, that is, a Co-Cr alloy containing 9.0 to 22.5% by weight of Cr, with the remainder consisting of Co and unavoidable impurities. As a result of conducting research from a materials perspective in order to resolve the temporal decline in saturation magnetization that occurs when a Co-Cr alloy is used as a magnetic recording medium, we found that this Co-Cr alloy contains Ru 0.01 to 2 as an alloy component. .0% and Zr:
When one or two of Ti: 0.1 to 2.0% and Ti: 0.1 to 2.0% are contained, the resulting Co-based alloy has the following properties when used as a magnetic recording medium: The decrease in saturation magnetization over time is extremely small, and this C
When the O-based alloy contains A1: 0.1 to 2.0%,
We have obtained the knowledge that the decline in saturation magnetization over time becomes suppressed as the material becomes more advanced. Therefore, the present invention has been made based on the above findings, and the present invention is based on the above-mentioned findings, and includes a CO-based alloy for magnetic recording media containing Cr: 9.0 to 22.0% by weight.
5%, RU: 0.01-2.0%, and Z
Contains one or two of r: 0.1 to 2.0% and T1: 0.1 to 2.0%, and further contains A as necessary.
1:0.1 to 2.0%, with the remainder consisting 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 within the practical range of 80 to 850.
It has a Gaussian adjustment effect, but its content is 9.0%.
If the content is less than 22.5%, the saturation magnetization will be too high, exceeding 850 Gauss, and as a result, when used as a perpendicularly magnetized film, for example, magnetization perpendicular to the film surface will not be possible.On the other hand, if the content exceeds 22.5%, Only a saturation magnetization of less than 80 Gauss can be obtained, and as a result, the reproduction output becomes small and the S/N ratio worsens, making it unusable for practical use. Therefore, the content was reduced to 9.
．． It was set at 0 to 22.5%.

(b) RU The Ru component has the effect of suppressing the decline in saturation magnetization over time as described above, but if its content is less than 0.01%, the desired effect cannot be obtained; When the Cr content exceeds 2.0%, not only does the above-mentioned effect tend to deteriorate again, but when the Cr content is relatively high, it is difficult to secure a practical saturation magnetization of 80 Gauss or more. Since it disappears, its content should be reduced to 0.01 to 2.0.
%.

(c) Zr and Tj These components have the effect of preventing the saturation magnetization from decreasing over time when they coexist with Y, but
If the content is less than 0.1%, the desired effects cannot be obtained, while if the content exceeds 2.0%, not only will the effects tend to deteriorate, Since a practical saturation magnetization of 80 Gauss or more cannot be obtained with a high Cr content, the content was determined to be 0.1 to 2.0%, respectively.

(d) Al Furthermore, if Al is included, the deterioration of saturation magnetization over time will be suppressed, so it may be included as necessary, but if the content is less than 0.1%, the desired suppressing effect will not be achieved. On the other hand, if the Cr content exceeds 2.0%, it becomes difficult to secure a practical saturation magnetization of 80 Gauss when the Cr content is relatively high. It was set at .1 to 2.0%.

Next, the CO-based alloy of the present invention will be specifically explained using examples.

Examples CO-based alloys 1 to 18 of the present invention and Comparative Q, 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 these ingots were used to obtain a diameter of 1257T! nφ×thickness: 1.5W$
A sputtering target with dimensions L was prepared, and sputtering was then performed using these targets under the conditions of an atmosphere of high purity Ar and an atmospheric pressure of 8 x 10-3 t0rr to form a sputtering target with a thickness of 7 μm. A thin film serving as a magnetic recording medium having substantially the same composition as the alloy composition and having a thickness of 0.8 μm was formed on the surface of the Variester film substrate.

In addition, all of the comparative zero group alloys 1 to 4 have compositions in which the content of any one of the constituent components (indicated with an asterisk in Table 1) is outside the scope of this invention. It is something that we have. Next, the saturation magnetization of the various magnetic tapes obtained as a result was measured immediately after manufacture and 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. Then, 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 an applied magnetic field of 12K.
It was measured under the condition of 0e. From the results shown in Table 1, 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, and the practical use of 80 to 850 Gauss. Ru. Z
In a magnetic tape (corresponding to a conventional magnetic tape) using Comparative CO-based Alloy 1, which does not contain Ru and Tj, as a magnetic recording medium, the saturation magnetization decreases significantly over time; ．． Comparative zero base alloy 2, in which the contents of zrl and Ti are high, respectively, out of the scope of the present invention.
In the magnetic tapes using No. 3 and No. 4, both exhibited saturation magnetization of only 80 Gauss or less, 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 it is used as a magnetic recording medium, there is very little decrease in the saturation magnetization over time, so the signal level for recording and reproduction in magnetic recording can be maintained at a constantly high level. It is possible to maintain the

Claims (1)

[Claims] 1 Cr: 9.0-22.5%, Ru: 0.01-2.
0% and one or two of Zr: 0.1 to 2.0% and Ti: 0.1 to 2.0%, with the remainder consisting of Co and inevitable impurities ( % by weight or more) and exhibits very little deterioration in magnetic properties over time when used as a magnetic recording medium. 2 Cr: 9.0-22.5%, Ru: 0.01-2.
0%, and also contains one or two of Zr: 0.1 to 2.0% and Ti: 0.1 to 2.0%, and further Al: 0.1 to 2.0%. % and the rest is C
having a composition (more than % by weight) consisting of o and unavoidable impurities,
A Co-based alloy that exhibits very little deterioration in magnetic properties over time when used as a magnetic recording medium.