JPS59162250A - Magnetic alloy - Google Patents

Abstract

PURPOSE:To obtain a magnetic alloy for a magnetic recording medium with superior noise characteristics by substituting Co for part of Fe in a Tb-Fe alloy and Dy for part of Tb. CONSTITUTION:An alloy having a composition consisting of, by atom, 2-35% Co, 4-75% Fe, 10-40% Dy and the balance Tb is refined and cast into an ingot. The ingot is cut to a suitable shape and size to form a target for sputtering, and by using the target an amorphous thin film of 1,300Angstrom thickness is formed on a glass substrate. A magnetic alloy for a magnetic recording medium with superior uniaxial magnetic anisotropy, superior coercive force, low magnetostriction and improved noise characteristics is obtd.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to magnetic alloys, and more specifically, terbium (T), which has excellent noise characteristics and is effective for use in magnetic recording media.
b)-Dysprosium CD>')-Iron (Fe)-Cobalt (Co) based magnetic alloy.

[Technical background of the invention and its problems]

Generally, a magnetic recording medium in which the axis of easy magnetization of the magnetic layer is aligned perpendicular to the substrate surface is suitable for high-density recording because its self-demagnetization is small. In particular, the cue point (Tc)
The thin film of the magnetic recording medium described above, whose temperature is slightly higher than room temperature, is expected to be used as a high-density magneto-optical recording medium.

A magneto-optical recording medium is a magnetic optical recording medium that records information turns by irradiating the medium with light (radical) to generate inverted magnetic domains, and then measures the original Kerr rotation angle to record the recorded information. It is a recording medium that can read sounds.

Currently, the thin film of such magneto-optical recording media is M
Polycrystalline metal thin films represented by nB+, compound single crystal thin films represented by GIG (gadolinium iron garnet), and amorphous metal thin films such as Gd-Fe and Tb-Fe are known.

Among these, polycrystalline metal thin films such as MnB1 have a large coercive force of several KOe at room temperature and are therefore excellent as magnetic recording media.
In the case of nB1, Tc = 360°C) writing requires a large amount of energy, and since it is polycrystalline, it is technically difficult to create a thin film with a stoichiometric composition. have.

Further, compound single crystal thin films typified by GIG are extremely expensive to manufacture and are extremely difficult to put into practical use industrially.

Amorphous metals such as Gd-Fe, MnB1, GI
Unlike G, it is amorphous, so it is easy to form a thin film on the surface of a suitable substrate, and it has the advantage that Tci can be controlled to some extent by adding some impurities. It has the disadvantage that the retention force at room temperature is small (300 to 5000e) and the recorded information is unstable. Of these amorphous metal thin films, it is said that the 'rb-Fe based ones have a significantly larger retention force (several KOe) than the Gd-Fe based ones due to the strong one-ion anisotropy of Tb. Because it has the characteristics
Tb--Fe based materials are attracting attention as magnetic recording media, especially as magneto-optical recording media.

-However, this 'rb-Fe-based magnetic alloy has a large magnetostriction constant (saturation magnetostriction constant, λ5) IXIO), and when used as a magnetic recording medium, it has a big problem in terms of noise characteristics.

That is, when manufacturing a thin film of a magnetic recording medium from a Tb-Fe based magnetic alloy, if internal stress (σ) is generated in the thin film of the medium for some reason, the σ direction caused by the reverse effect of magnetostriction Magnetic anisotropy energy between (Kσ - λS・σ)
Based on this, physical properties such as anisotropy of the thin medium film become microscopically non-uniform, resulting in a decrease in the SIN ratio. For example, when a thin film of Tb-Fe magnetic alloy is formed on a substrate by the bias sputtering method, the internal stress of the thin film fluctuates due to variations in the gas pressure in the bell jar and the bias voltage during sputtering. A problem has arisen in that the physical properties of the thin film are microscopically non-uniform and its noise characteristics are significantly degraded.

[Purpose of the invention]

The present invention provides a magnetic recording medium which has excellent -axis magnetic anisotropy and coercive force characteristics, and has low magnetostriction and has significantly improved noise characteristics.
In particular, the object is to provide a magnetic alloy that is effective for use in magneto-optical recording media.

[Summary of the invention]

In order to achieve the above object (as a result of extensive research into the composition and structure of Tb-Fe alloys, the present inventors found that replacing part of Fe with fco reduces the λS of the alloy; When Dy is substituted, the resulting alloy undergoes zero magnetostriction and becomes λ
The new fact that S becomes negative led us to develop the magnetic alloy of the present invention.

That is, the magnetic alloy of the present invention is characterized by having a composition of 2 to 35 atoms of Co, 40 to 75 atoms of Fe, 10 to 40 atoms of Dy, and the balance essentially being Tb.

In the composition of the magnetic alloy of the present invention, CO is an element that contributes to the reduction of λS, but if the content is less than 2 atoms, the decrease in λS will not be significant and the object of the present invention will not be achieved. . Moreover, if it exceeds 35 at.

If the content of Fe is less than 40 atoms, λS will increase and the coercive force will decrease, and even if it exceeds 75 atoms q6e, the effect of reducing λS will not be sufficient, so it should be set to 40 to 75 atoms. Set.

If Dy is less than 10 atoms, the reduction in λS of the alloy will be insufficient, and if it exceeds 40 atoms, the coercive force will decrease, so Dy is set in the range of 10 to 40 atoms. .

In the magnetic alloy of the present invention, the remainder is Tb and unavoidable mixed components. Tb is an essential component for completely improving perpendicular magnetic anisotropy and coercive force characteristics.

The magnetic alloy of the present invention is usually put to practical use in the form of a thin film or powder, but it is preferably used in the form of an i# film because high-density magnetic recording is possible.

The structure of the alloy may be polycrystalline, single crystal, or amorphous, but in the case of crystalline and polycrystalline structures, the grain boundaries constitute a source of nonuniformity in physical properties and affect noise characteristics. Therefore, it is preferable to be amorphous.

The magnetic alloy of the present invention is obtained by melting an alloy material having the above-mentioned composition by heating it to a temperature above its melting point in a vacuum, an inert gas such as Ar or He, or a reducing gas atmosphere such as H2 or CO, using a well-known method. After cooling, it can be easily prepared as an ingot.

In order to form a thin film for a magnetic recording medium from this ingot, for example, the ingot is first cut into appropriate dimensions and shapes to form a sputtering target, and this is used to sputter or sputter onto, for example, a glass substrate. Bye.

[Embodiments of the invention]

Example 1 Co 13.2 at%, Fe63.8 at%, Dy20
．． An alloy material having 0 atoms and the remainder being substantially Tb was melted in a full vacuum induction melting furnace (1500°C) and then cooled to form an alloy ingot. Next, I cut out targets for snow and ivy from this ingot.

Using this targrater, the argon gas pressure is 6×10-'
A thin film with a thickness of 1300 A was formed on a glass substrate by a bias sputtering method using Torr and a substrate bias voltage of -50 V. The thin film was amorphous.

This thin film has perpendicular magnetic anisotropy and saturation magnetic flux density (4y
rMs) is 9 Q Q Gauss, retention force (IHC)
is 7KOe.

The cue temperature (Tc) was 150°C, and the saturation magnetostriction (λS) was less than 1×10.

For comparison, a film with a thickness of 1100A was prepared in the same manner as above except that 80 atoms of Fe were used and the remainder was substantially Tb.
A Tb-Fe amorphous thin film was formed as Comparative Example 1. 4πMs of this thin film is 700 Gauss +IH
c is 5 KOe, Tc is 110℃, λS is 1000
It was a dog from X 10-6.

Table 1 shows the specifications of the rewritable disk when the two types of thin films mentioned above are used as a magnetic recording medium.

Examples 2 to 6 Nine types of alloy materials with various compositions (atomic) as shown in Table 2 were prepared, and amorphous magnetic alloy thin films were entirely formed using the same methods as in Example 1. All of these properties are listed together in Table 2.

〔Effect of the invention〕

As is clear from the above explanation, the magnetic alloy of the present invention has:
Since the absolute value of λS is smaller than lX1O-6, microscopic fluctuations in magnetic anisotropy due to internal stress during processing (for example, during thin film formation) do not occur, and the uniformity of physical properties is maintained. When applied as a magnetic recording medium, the S/N ratio increases and noise characteristics are excellent. In particular, in the case of magneto-optical recording media, it is possible to completely prevent the deterioration of the characteristics of the medium due to thermal disturbances during magneto-optical writing (thermal magnetism).
Due to the effect of added Co, the Kerr rotation angle of the magneto-optical recording medium becomes sharper, and the synergistic effect with the above-mentioned (2) significantly improves the noise characteristics. (2) Furthermore, since the magnetic alloy of the present invention is a Tb-based alloy with one ion anisotropy, it also has excellent uniaxial magnetic anisotropy and coercive force characteristics. (2) Since Tc is within the range of 50 to 200° C., large energy is not required for magneto-optical writing.

In view of the above points, the magnetic alloy of the present invention is particularly effective when applied to magneto-optical recording media, and its industrial value is extremely large.

Claims (1)

Claims: 1. A magnetic alloy comprising 2 to 35 atoms of cobalt, 40 to 75 atoms of iron, 10 to 40 atoms of dysprosium, and the remainder substantially terbium. 2. The magnetic alloy according to claim 1, wherein the magnetic alloy is in the form of a thin film. 3 Claim-1 in which the magnetic alloy is an amorphous alloy
The magnetic alloy according to item 1 or 2.