JPS6047893B2 - 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 decline in magnetic properties, especially saturation magnetization, over time when used as a magnetic recording medium.
There is something about 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. 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 to 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 degrading. 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 developed the above-mentioned Co-Cr alloy, which is conventionally used as a magnetic recording medium, that is, Cr: 9.0 to 2.
Focusing on a Co-Cr alloy with a composition of 2.5% by weight and the remainder consisting of Co and unavoidable impurities,
As a result of conducting research from a materials perspective in order to solve the problem of the -Cr alloy, that is, the decrease in saturation magnetization over time that occurs when this Co-Cr alloy is used as a magnetic recording medium,
This Co-Cr alloy contains 0.01 Ru as an alloy component.
When the Ru-containing Co-Cr alloy is contained in an amount of ~2''% by weight, when it is used as a magnetic recording medium, the saturation magnetization decreases significantly over time.
Furthermore, they have found that by incorporating 0.5 to 2.0% by weight of river, it becomes possible to further suppress the decrease in saturation magnetization over time. The present invention has been made based on the above findings, and the present invention is based on the above findings, and includes a CO-based alloy for magnetic recording media having a Cr content of 9.0 to 22% by weight.
．． 5% by weight, RU: 0.01 to 2.0%, further containing A1: 0.5 to 2.0% as necessary, and the remainder consisting of CO and inevitable impurities. It has the following characteristics.

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 saturation magnetic flux density of the Cr component is within the practical range of 80 to 85.
It has the effect of adjusting to 0 Gauss, but its content is 9.0
If it is less than %, the saturation magnetization will be too high exceeding 850 Gauss, and as a result, when used as a perpendicular magnetization film, for example,
Magnetization alignment perpendicular to the film surface becomes impossible, while 22.

If the content exceeds 5%, a saturation magnetization of less than 80 Gauss will be obtained, resulting in a small reproduction output and a poor S/N ratio, making it unusable for practical use. It was set at ~22.5%.

(b) Ru The Ru component has the effect of suppressing the decrease in saturation magnetization over time as described above, but if its content is less than 0.01%, the desired effect cannot be obtained; If the Cr content exceeds 0.0%, it becomes impossible to secure a practical saturation magnetization of 80 Gauss or more, especially when the Cr content is high. Therefore, the content is set at 0.01 to 2.0%. Ta.

(C) The AlAl component has the effect of further suppressing the decrease in saturation magnetization over time in coexistence with the Y component, so it is contained as necessary, but its content is 0.

If it is less than 5%, the desired improvement in the above effect cannot be obtained;
．． If the content exceeds 0%, it becomes difficult to secure a practical saturation magnetization of 80 Gauss or more when the Cr content is high, similar to the Y component, so the content is set to 0.

It was set at 5 to 2.0%. Next, the CO-based alloy of the present invention will be explained using examples and comparing with comparative examples.

Example 1 Inventive CO-based alloys 1 to 12 and comparative CO alloys having the compositions shown in Table 1 were prepared by a conventional melting and casting method.
Prepare ingots of base alloys 1 and 2 respectively), and then from these ingots diameter: 125T1rmφ x thickness: 1.5m
A sputtering target with a dimension of n was prepared, and high-frequency sputtering was performed using these targets under the conditions of an atmosphere of Ar'' gas and an atmospheric pressure of 2 x 10-2' TOrr to form a polyester film with a thickness of 7 PTrL. A thin film serving as a magnetic recording medium having substantially the same composition as the alloy composition and having a thickness of 0.5 PTr1 was formed on the surface of the substrate.

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 shown in the first volume. Note that the saturation magnetization was measured using a vibrating sample type magnetic measurement device with an applied magnetic field of 5K0.
It was measured under the conditions of e. As is clear from the results shown in Table 1, each of the magnetic recording media is CO-based alloy 1 of the present invention.
In the magnetic tapes composed of 1 to 12, the decrease in saturation magnetization over time was extremely small, whereas in the magnetic tapes composed of comparative CO-based alloy 1, which does not contain Ru and corresponds to conventional magnetic recording media, The decrease in saturation magnetization over time has become extremely significant. Furthermore, it is shown that practical saturation magnetization cannot be obtained in a magnetic tape using comparative zero group alloy 2 with a high Ru content outside of this range.
◆Example 2 Using the CO-based alloys 1 to 12 of the present invention prepared in Example 1 and comparative CO-based alloys 1 and 2, a target for magnetron sputtering was created from these, and using this target, atmosphere: Ar gas. , Atmospheric pressure: 1 x 10-2t0rr1 Magnetic flux density above the target: 5
A magnetic recording medium having a thickness of 0.3 PrrL and having substantially the same composition as the alloy was formed on the surface of a polyamide substrate having a thickness of 77 μm by performing magnetron sputtering and dividing by 7 μm under the condition of 0.00 Gauss. A thin film was formed.

The saturation magnetization of the resulting magnetic disk was measured under the same conditions as in Example 1.

These results are shown in Table 2. As shown in Table 2, Example 2 also showed the same results as Example 1, and the CO of the present invention containing Ru and further containing N
It is shown that when base alloys 1 to 12 are used as magnetic recording media, the decrease in saturation magnetization over time is significantly small.

Example 3 CO-based alloy 1 of the present invention also prepared in Example 1
~12 and Comparative CO-based alloys 1 and 2, these alloys were made into a shot with a diameter of 2 Wf, and this shot was placed in a graphite crucible, and the atmosphere: Ar gas, atmosphere:
Vacuum deposition was performed under the conditions of ×10-3t0rr, and the diameter:
127wftφ×Thickness: 0.8-layer A1 alloy substrate surface with substantially the same composition as the alloy Thickness: 0.2μ
A thin film of m as a magnetic recording medium was formed.

Then, the saturation magnetization of the various magnetic disks obtained as a result was measured under the same conditions as in Example 1.

These results are shown in Table 3. As shown in Table 3, this Example 3 also showed the same results as in Example 1, and the CO-based alloys 1 to 12 of the present invention containing Ru and further containing A1 were used as magnetic recording media. In conventional magnetic disks, Ru
It is clear that the decrease in saturation magnetization over time is extremely small compared to the case where Comparative Alloy 1, which does not contain 3, is used.

As mentioned above, when the CO-based alloy of the present invention is used as a magnetic recording medium, the saturation magnetization decreases over time very little, so the recording/reproducing signal level in magnetic recording can be maintained at a high level at all times. There are some things you can do.

Claims (1)

[Claims] 1 Cr: 9.0-22.5%, Ru: 0.01-2.
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. 2 Cr: 9.0-22.5%, Ru: 0.01-2.
0%, further contains Al: 0.5 to 2.0%, and the remainder is Co and inevitable impurities (more than 1% by weight)
) and exhibits extremely little deterioration in magnetic properties over time when used as a magnetic recording medium.