JPS6056413B2 - 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 with a composition 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 decrease 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 0.001 to 0 Y .10%,RU:
When 0.01 to 2.0% is contained, the resulting Co-based alloy exhibits significantly less decrease in saturation magnetization over time when used as a magnetic recording medium. Zr: 0.1-2.0%, Ti: 0.1
~2.0%, and Al: 1 of 0.1~2.0%
They have found that when one or more species are contained, the decline in saturation magnetization over time can be suppressed. Therefore, the present invention has been made based on the above knowledge, and the present invention is based on the above-mentioned findings.
Contains 1 to 0.10%, RU: 0.01 to 2.0%,
Furthermore, if necessary, Zr: 0.1 to 2.0%, Ti: 0
．． 1 to 2.0%, and one or more of A1: 0.1 to 2.0%, with the remainder consisting of CO and inevitable 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 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 perpendicular magnetization film, it will be impossible to achieve magnetization orientation perpendicular to the film surface. Since only a saturation magnetization of less than 80 Gauss can be obtained, resulting in a small reproduction output and a poor S/N ratio, making it unusable for practical use, the content is set at 9.0 to 22.5%. Ta.

(b) Y and Ru Both of these components have the effect of suppressing the decrease in saturation magnetization over time, and their contents are respectively . Y: 0.001%
If Y: less than 0.01% or RU: less than 0.01%, the desired effect of suppressing the decrease in saturation magnetization over time cannot be obtained, while Y: 0.1%.
When the content exceeds 0% and RU:2.0%, not only does the above effect tend to decrease again, but when the Cr content is relatively high, the practical saturation magnetization exceeds 80 Gauss. Since it becomes impossible to secure the content, the content should be adjusted to Y: 0.001 to 0.
10% and RU: 0.01 to 2.0%.

(c) Zr, TI, and A1 These components have an even effect of further suppressing the decline in saturation magnetization over time when they coexist with Y and Ru, so they are included as necessary. The content is Zr:0.1, respectively.
If Zr: less than 0.1, Tl: less than 0.1, and A1: less than 0.1, the desired effect of improving the above action cannot be obtained;
Even if the content exceeds 0%, Ti: 2.0%, and AI: 2.0%, the effect of improving the so layer will appear.
Moreover, if the Cr content is relatively high, it is impossible to secure a practical saturation magnetization of 80 Gauss or more.
The contents are Zr: 0.1-2.0%, T
i: 0.1-2.0%, and A1: 0.1-2.0%
It was determined that

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-based alloys 1 to 3 were prepared, and then diameter: 125wLφ x thickness: 1.5Tr$t was prepared from these ingots.
Fabricate a sputtering target with dimensions of
Subsequently, using these targets, atmosphere: Arl
Sputtering was performed under atmospheric pressure conditions of 5 x 10-3 t0rr to form a 0.6 μm thick magnetic recording medium having substantially the same composition as the alloy composition on the surface of a 7 μm thick polyester film substrate. A thin film was formed.

In addition, all of the above comparative CO-based alloys 1 to 3 have compositions in which the content of one of the constituent components (indicated with an asterisk in Table 1) is outside the scope of the present invention. It is something. 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. , 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 10K.
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 is observed. Whereas saturation magnetization is maintained over a long period of time, magnetic tape (corresponding to conventional magnetic tape) using comparative zero-base alloy 1, which does not contain Y or Ru, as a magnetic recording medium retains saturation magnetization over time. The decline was extremely significant, while Y
Ratio 11! in which the content of Ru and Ru content is high and out of the scope of the present invention! In the magnetic tapes using f: and o-based alloys 2 and 3, the saturation magnetization was less than 80 Gauss, and practical saturation magnetization could not be obtained. As mentioned above, when the CO-based alloy of the present invention is used as a magnetic recording medium, the saturation magnetization decreases very little over time, so the recording/reproducing signal level in magnetic recording can be maintained at all times. There are some things you can do.

Claims (1)

[Claims] 1 Cr: 9.0-22.5%, Y: 0.001-0.
10%, Ru: 0.01-2.0%, 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. 2 Cr: 9.0-22.5%, Y: 0.001-0.
10%, Ru: 0.01-2.0%, and further contains Z
Contains one or more of r: 0.1 to 2.0%, Ti: 0.1 to 2.0%, and Al: 0.1 to 2.0%, and the remainder is Co and unavoidable. A Co-based alloy that has a composition (the above weight %) consisting of impurities and whose magnetic properties show very little deterioration over time when used as a magnetic recording medium.