JPS6056412B2 - 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 rare earth metals: 0.001 were added to this CO-Cr alloy as an alloy component. ~0.10%
, MO: 0.5~2.0%, and Hf: 0.005~
When one or more of the above 0.10% is contained, the resulting CO-based alloy exhibits significantly less decrease in saturation magnetization over time when used as a magnetic recording medium. CO-based alloy, Y: 0.001-0
．． 10%, RU: 0.01~2.0%, Zr: 0.1~
2.0%, Ti: 0.1-2.0%, and Al: 0.
They have found that when one or more of 1% to 2.0% of the content is contained, the decline in the sawing stage and 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 2.5% and rare earth metal: 0.001~
0.10%, MO: 0.5-2.0%, and Hf: 0
．． 005'-0.10%, and further contains Y: 0.001 to 0.10 as necessary.
%, Ru: 0.01-2.0%, Zr: 0.1-2.0
%, Ti: 0.1-2.0%, and A1: 0.1-2
．． It is characterized by a composition in which it contains one or more of 0% and the rest is 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 a Gaussian adjustment effect, but its content is 9.0%.
In the past, the saturation magnetization was too high, exceeding 850 Gauss, and as a result, for example, when used as a perpendicular magnetization film,
Magnetization orientation perpendicular to the film surface becomes impossible, while 22.5%
If the content exceeds 80 Gauss, only 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. Therefore, the content was set at 9.0 to 22.5%.

(b) Rare earth metal, MOL, and Hf These components have the same effect of suppressing the decline in saturation magnetization over time as described above, but the content of each is rare earth metal: 0.001% Less than 0.5% of MO, and less than 0.005% of Hf will not produce the desired effect;
If the content exceeds 2.0% of Hf and 0.10% of Hf, not only does the above-mentioned effect tend to decrease, but especially when the Cr content is relatively high, the Cr content exceeds 80 Gauss. Since it becomes impossible to secure practical saturation magnetization of
and Hf: 0.005 to 0.10%.

・(c)Y,. Ru,. Zr. , Til and Al These components have an even effect of further suppressing the decline in saturation magnetization over time in coexistence with the components shown in item (b) above, so they are included as necessary. However, the content is Y: less than 0.001%, RU: 0.
When Y: less than 0.1%, Zr: less than 0.1%, Ti: less than 0.1%, and A1: less than 0.1%, no significant improvement effect on the above action can be obtained, while Y: 0.10% and RU: less than 0.1%, respectively. :
2.0%, Zr: 0.1-2.0%, Ti: 0.1%,
And A1: Even if the content exceeds 2.0%, the effect of improving the Cr layer will appear.In fact, if the Cr content is high, it will be difficult to secure a practical saturation magnetization of 80 Gauss or more. , the content is Y: 0.001, respectively.
~0.10%, RU: 0.01~2.0%, Zr: 0.
1-2.0%, T1: 0.1-2.0%, and A1:
It was set at 0.1 to 2.0%.

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

Examples CO-based alloys 1 to 40 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-based alloys 1 to 4 were prepared respectively, and then diameter: 125wrmφ x thickness: 1.5Tm1 was prepared from these ingots.
A sputtering target with a dimension of n was prepared, and then magnetron sputtering was performed using these targets under the conditions of atmosphere: high-purity Ar and atmospheric pressure of 3 x 10-3 t0rr, and thickness: 7 μm. A thin film as a magnetic recording medium having substantially the same composition as the alloy composition and having a thickness of 0.3 μm was formed on the surface of a polyester film substrate.

In addition, all of the above comparative CO-based alloys 1 to 4 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, 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.

Claims (1)

[Claims] 1 Contains 9.0 to 22.5% of Cr, 0.001 to 0.10% of rare earth metals, and 0.5 to 2.5% of Mo.
0%, and Hf: 1 of 0.005-0.10%
A Co-based alloy having a composition (by weight %) containing one or more species and the remainder consisting of Co and unavoidable impurities, and which exhibits extremely little deterioration in magnetic properties over time when used as a magnetic recording medium. 2 Cr: 9.0-22.5%, rare earth metal: 0.001-0.10%, Mo: 0.5-2.
0%, and Hf: 1 of 0.005-0.10%
Contains one or more species, further Y: 0.001 to 0
．． 10%, Ru: 0.01~2.0%, Zr: 0.1~
2.0%, Ti: 0.1-2.0%, and Al: 0.
1 to 2.0%, and the remainder is Co and unavoidable impurities (weight%), and when used as a magnetic recording medium, the magnetic properties change over time. Co-based alloy with very little loss of performance.