JPS58113340A - Co alloy for magnetic recording medium - Google Patents

Abstract

PURPOSE:To considerably reduce the deterioration of the magnetic characteristics, especially the saturation magnetizability of a Co alloy due to aging when the alloy is used as a magnetic recording medium, by providing a specified composition contg. Cr and a small amount of Y. CONSTITUTION:This Co alloy for a magnetic recording medium has a composition consisting of, by weight, 9.0-22.5% Cr, 0.001-0.1% Y and the balance essentially Co or further contg. 0.5-2.0% Al.

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.
It concerns 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 a plastic film or a metal sheet on the surface of the substrate.
For example, cr:9. o~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 into 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. This undermined credibility. 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 developed the above-mentioned C0-Cr alloy conventionally used as a magnetic recording medium, that is, containing 9.0 to 22.5% by weight of Cr,
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 a materials perspective 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 Y was added to this Co-Cr alloy as an alloying component from 0.001 to 0.001. 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~
They found that containing 2.0% by weight of arsenic makes it possible to further suppress the decline in saturated box magnetization over time.

This invention has been made based on the above findings, and includes a Co-based alloy for magnetic recording media with a weight M% of Cr: 9.
．． 0-22.5%, Y: 0.001-0.1%
The composition is characterized in that it further contains M: 0.5 to 2.0 as necessary, and the remainder consists 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 Does the Cr component have the effect of adjusting the saturation magnetization to a practical range of 80 to 850 Gauss? If its content is less than 9.0%, the saturation magnetization exceeds 850 Gauss and becomes 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 N ratio will deteriorate, making it impossible to put it into practical use, the content should be set at 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 if the content thereof is less than 0001, the desired effect cannot be obtained; If the content exceeds .1%, it is impossible to obtain a practical saturation magnetization of 80 Gauss or more, especially when the Cr content is high.
Its content was determined to be 1 to 0.1% of O,OO.

(c) Ai The AA acid component has the effect of further suppressing the decline in saturation magnetization over time in coexistence with the Y component, so it is included as necessary, but if the content is less than 0.05%, the above effect will be reduced. On the other hand, if the content exceeds 20%, it will be difficult to secure a practical saturation magnetization of 80 Gauss or more when the Cr content is high, similar to the Y component. Its content is set at 0.5 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 Go-based alloy-11 and comparative Co, each having the composition shown in Table 1, were prepared by a normal melting and casting method.
Ingots of base alloys 1 and 2 were respectively prepared, and subsequently targets for sputtering logs with dimensions of diameter: 125gφ x thickness: 1.5mm were created from these ingots, and using these targets, High-frequency sputtering was performed under the conditions of HAr gas atmosphere and atmospheric pressure of 2 X I Q-torr, and a 1058 m thick magnetic film with substantially the same composition as the alloy was deposited on the surface of a polyester film substrate with a thickness of about μm. A thin film was formed as a recording medium.

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 also shown in Table 1. Note that the saturation magnetization was measured using a vibrating sample type magnetic measuring device under the conditions of applied magnetic field: 5 KOe.

As is clear from the results shown in Table 1, in the magnetic tapes in which the magnetic recording medium was composed of the CO-based alloys 1-11 of the present invention, the decrease in saturation magnetization over time was significantly small. Comparative C, which does not contain Y, corresponds to a conventional magnetic recording medium.

In the magnetic tape made of base alloy 1, the saturation magnetization decreases significantly over time. 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 Invention CO-based alloys 1 to 11 prepared in Example 1 and comparative CO-based alloy 1. 2, a magnetron sputtering target was created from this, and this target was used to create an atmosphere: Ar gas, atmospheric pressure of crab I X 10.
torr1 target) Magnetron sputtering was performed under the conditions of upper magnetic flux 1 degree: 500 Gauss, and the thickness was 77 mm.
A thin film serving as a magnetic recording medium having a thickness of 03 μm and having substantially the same composition as the alloy composition was formed on the surface of a polyamide substrate having a thickness of 0.03 μm.

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. Table 2 As shown in Table 2, the magnetic disks in which the magnetic recording medium was made of the Co-based alloys of the present invention] to 11 had a higher magnetic recording capacity than the magnetic disks using the comparative Co-based alloy 1, which did not contain Y. It has been shown that the decrease in saturation magnetization over time is extremely small.

Example 3 Same <Invention Co-based alloys 1 to 11 prepared in Example 1 and comparative Co-based alloy 1. 2, make these alloys into shots with a diameter of 211, put this shot into a graphite crucible, atmosphere: Ar gas, atmospheric pressure crab I
Vacuum deposition was performed under conditions of -torr, and a 10.2 μm thick film having substantially the same composition as the alloy was deposited on the surface of an M alloy substrate with a diameter of 2127 mm and a thickness of 0.8 mm.
A thin film was formed as a magnetic recording medium.

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 1.2, and Table 3 Co-based alloys 1 to 1 of the present invention containing Y and further containing M
In the magnetic disk using No. 11 as a magnetic recording medium, Comparative C which does not contain Y, which corresponds to the conventional magnetic recording medium.
It is clear that the decrease in saturation magnetization over time is extremely small compared to the case where o-based alloy 1 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 very little over time, so the signal level for recording and reproduction in magnetic recording can be kept constantly high. It is possible to retain it.

Applicant: Mitsubishi Metals Corporation Agent Tomi 1) Kazuo

Claims (2)

[Claims] (1) Cr: 9.0-22.5%, Y
: Contains 0.001-0.1%, the rest is CO
A Co-based alloy which has a composition (the above weight %) consisting of unavoidable impurities and whose magnetic properties show very little deterioration over time when used as a magnetic recording medium. (2) Cr2 9. O~22shi, 5%, Y: 0.001~0
．． Contains 1% and further has an AQ: O,,5-2.
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.