JPS6047894B2 - 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.

Traditionally, magnetic disks, floppy disks,
Magnetic tape for audio, magnetic tape for VTRs, magnetic photographic disks, and magnetic tape for computers are processed by surface treatments such as sputtering, vacuum evaporation, and chemical plating on the surface of substrates such as plastic films and metal sheets. For example, Cr: 9.0~
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 22.5% 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 Co
- Cr alloy magnetic recording media have a problem in that the initial saturation magnetization gradually decreases over time, which results in a decrease in the recording/reproducing signal level in magnetic recording and impairs reliability. It was hot.

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 created the above-mentioned Co-Cr alloy, which is conventionally used as a magnetic recording medium, that is, contains Cr: 9.0 to 22.5% by weight,
Co- with a composition in which the remainder consists of Co and unavoidable impurities
Focusing on Cr alloy, problems with this Co-Cr alloy,
That is, as a result of conducting research from the material aspect in order to solve the temporal decrease in saturation magnetization that occurs when this Co-Cr alloy is used as a magnetic recording medium, we found that 0.001 Y was added to this Co-Cr alloy as an alloy component. When the Y-containing Co-Cr alloy is contained in an amount of ~0.1% by weight, when used as a magnetic recording medium, the saturation magnetization decreases significantly over time. 0.5~2
．． They have found that by containing 0% by weight, it is 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, in which a CO-based alloy for magnetic recording media is prepared with Cr:9.
0 to 2.5%, Y: 0.001 to 0.1%, further containing A1: 0.5 to 2.0% as necessary, and the remainder consisting of CO and inevitable impurities. It is characterized by its structure.

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 the effect of adjusting the saturation magnetization to a practical range of 80 to 850 Gauss, but if its content is less than 9.0%, the saturation magnetization will exceed 850 Gauss and become too high.
As a result, for example, when used as a perpendicularly magnetized film, it becomes impossible to mix the magnetization perpendicular to the film surface.On the other hand, when the content exceeds 22.5%, only a saturation magnetization of less than 80 Gauss is obtained, resulting in reproduction. Since the output will decrease and the S/N ratio will deteriorate, making it unusable, the content should be 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 its content is 0.

If the content is less than 0.001%, the desired effect cannot be obtained, while if the content exceeds 0.00%, it is impossible to obtain a practical saturation magnetization of 80 Gauss or more, especially when the Cr content is high. The content was determined to be 0.001 to 0.1%.

(c) Al The Al component has the effect of further suppressing the decline in saturation magnetization over time when coexisting with the Y component, so it is included as necessary, but its content is less than 0.5%. However, if the content exceeds 2.0%, a practical saturation magnetization of 80 Gauss or more is secured when the Cr content is high like the Y component*8. Since it becomes difficult to do so, the content should be set at 0.5 to 2.
It was set as 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 11 and comparative CO alloys having the compositions shown in Table 1 were prepared by a conventional melting and casting method.
Ingots of base alloys 1 and 2 were respectively prepared, and then from these ingots diameter: 125Tr0nφ x thickness: 1.5?
Create a sputtering target with dimensions of
Using these targets, high-frequency sputtering was performed under the conditions of Ar gas atmosphere and atmospheric pressure of 2 x 10-2 t0rr to form a component composition substantially the same as the alloy composition on the surface of a polyester film substrate with a thickness of 7 μm. A thin film was formed as a magnetic recording medium with a thickness of 0.5 μm.

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 Table 1. Note that the saturation magnetization was measured using a vibrating sample type magnetic measurement device with an applied magnetic field of 5K0e.
Measured under the following conditions. It is shown in Table 1. As is clear from the results, each of the magnetic recording media is CO-based alloy 1 of the present invention.
In the magnetic tapes composed of 1 to 11, the decrease in saturation magnetization over time was extremely small, whereas the comparative CO-based alloy 1 which does not contain Y, which corresponds to conventional magnetic recording media,
In magnetic tapes constructed of the above, the saturation magnetic drop has become extremely significant. Furthermore, it has been shown that practical saturation magnetization cannot be obtained in a magnetic tape using Comparative CO-based alloy 2, which has a high Y content outside the range of the present invention. Example 2 Using CO-based alloys 1 to 11 of the present invention and comparative CO-based alloys 1 and 2 prepared in Example 1, a target for magnetron sputtering was created, and this target was used to create an atmosphere: Ar gas, atmosphere. Pressure d1×10-2
Magnetron sputtering and ringing were performed under the conditions of t0rr", target upper magnetic flux density: 500 Gauss, and a thickness of 77 pTr1. A thin film as a magnetic recording medium having substantially the same composition as the alloy composition and having a thickness of 0.3p was formed on the surface of the polyamide substrate.

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, in magnetic disks in which the magnetic recording medium was made of CO-based alloys 1 to 11 of the present invention, comparative alloys 0
It is shown that the decrease in saturation magnetization over time is significantly smaller than that of the magnetic disk using Base Alloy 1.

Example 3 Using the present invention CO-based alloys 1 to 11 and comparative CO-based alloys 1 and 2, which were also prepared in Example 1, these alloys were made into diameters:
2Wr! This shot is placed in a graphite crucible, atmosphere: Ar gas, atmospheric pressure: 1 x 10-
Vacuum deposition was performed under the conditions of 3t(1)Rr, diameter:
127w1nφ×Thickness:0.8 Thickness with substantially the same composition as the alloy composition on the surface of the A1 alloy substrate: 0
．． A thin film of 2 pm 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 Examples 1 and 2, and the CO-based alloys 1 to 11 of the present invention containing Y and further containing Al were used as magnetic recording media. It is clear that in the magnetic disk used as a magnetic disk, the decrease in saturation magnetization over time is extremely small compared to the case of using Comparative QO-based alloy 1, which does not contain Y and corresponds to a conventional magnetic recording medium.

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 signal level for recording and reproducing in magnetic recording can be kept constantly high. It is possible to retain it.

Claims (1)

[Claims] 1 Cr: 9.0-22.5%, Y: 0.001-0.
A Co-based alloy having a composition (by weight %) containing 1% and the remainder consisting of Co and unavoidable impurities, and whose magnetic properties show very little deterioration over time when used as a magnetic recording medium. 2 Cr: 9.0-22.5%, Y: 0.001-0.
1%, 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 storage medium.