JPS6083305A - Magneto-optic medium - Google Patents

Abstract

PURPOSE:To obtain regenerative C/N wherein the Kerr rotation angle is increased and is appropriate in practical use by substituting Fe with Co and a rare earth element with another rare earth element in an Fe rare earth element 2 amorphous vertically magnetized film. CONSTITUTION:By substituting Fe with Co, the force-rotation angle is increased and by substituting a rare earth element with another rare earth element, the force-rotation angle is further increased, the performance coefficient is improved, a product Hc.Ms of coercive force Hc and saturated magnetization Ms which becomes a target of stability in the diameter of a recording bit is increased and an amorphous vertically magnetized film which has a curie temperature appropriate for practical use is obtained. In quantity (x) of substituting Fe with Co, to make the effect of increasing force-rotation angle more notable, 0.1 or more (x) is reguired and if x=0.4 or more, the curie temperature is raised to 230 deg. or higher. The value of a which shows the quantity of rare earth element shall also be 17<=a<=32. If (a) is out of this range, the amorphization of a medium tends to be prevented.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to magneto-optical recording in which information is recorded, reproduced and erased using laser light, and in particular improves the figure of merit by improving the Kerr rotation angle. Then, the reproduction SZN ratio or C/
This is a story about a magneto-optical medium with improved N ratio.

[Background of the invention]

Recently, magneto-optical recording, which has high density, large capacity, and allows arbitrary reading and rewriting of information, has been attracting attention.

In magneto-optical recording, a magnetic thin film (perpendicularly magnetized film) with an axis of easy magnetization perpendicular to the film surface is used, and by creating reversal magnetic domains at arbitrary positions with a light beam, the direction of one of them can be changed. Corresponding to this, binary information of 61" and 0" is recorded. On the other hand, the readout of binary signals subjected to such inversion recording is usually carried out using the Polar Kerr effect or the Faraday effect.

Conventionally, MnB1 was used as an optical medium.
Perpendicularly magnetized films have been proposed, such as crystalline films based on rare earth metals, amorphous thin films based on rare earth metals, and single crystal thin films typified by garnet. Among them, rare earth-transition metal-based amorphous thin films have no grain boundaries, have low media noise, and are easy to manufacture over large areas, so their current availability is considered promising. These rare earth-transition metal-based amorphous thin films include Gd Co, G”r
b-cO.

Gd Dy Co, Tb Fe, Tb Gd-Fe, T
b-1) y-Fe, Gd-Tb-Dy-pe, T
b -1i' e -CO, D y-Ii' e -
Alloy systems such as Co are currently being developed, and the Kerr rotation angle of the film itself has been improved to 0.4°. However, in order to obtain a reproduced signal level (C/N, -50 dB) for practical use, the Kerr rotation angle obtained with these alloy systems is insufficient, and the film itself must be improved to improve the C/N. There is a demand for improvement in car rotation angle.

[Purpose of the invention]

An object of the present invention is to provide an amorphous magneto-optic medium which has a Kerr rotation angle higher than that of the above-mentioned alloy systems and which provides a reproduction C/N ratio sufficiently suitable for practical use. : [Summary of the Invention] The present inventors have determined that the moment of the Fe element, which contributes to the Kerr rotation angle, in an Fe-rare earth@binary amorphous perpendicularly magnetized film can be changed by replacing Fe with Co. Shitakikushi, 1 more
By replacing the rare earth element, which is a constituent element of tt4, with another kind of rare earth element, the Kerr rotation angle is further improved, and at the same time, by optimizing the Curie temperature, the figure of merit v, which is proportional to the reproduction output level, is improved. 'Nθk (R is reflectance, θ
The present invention was developed based on the idea of improving the Kerr rotation angle.

In the magneto-optical medium of the present invention, T is a ferromagnetic rare earth element Q
Two elements selected from the group of d, Tb, and Dy.

The general formula is □(Fet-
It is a quaternary amorphous verticalized film represented by ICOX) too-aTa. , FeCo T b + FC-〇〇-Gd ternary system, when Fe is replaced with CO,
The fact that the Kerr rotation angle becomes extremely thick near the composition of li'e:Co=1:1 is explained by Tsunashirna et al.
.

AI)I)I, PhyS 53 (11) (19
82) I), 8175) or from the experimental results of Tsujimoto et al. (Journal of the Japanese Society of Applied Magnetics 7 (2+ (1983) p. 119).

However, in this case, where the Kerr rotation angle is large, the coercive force decreases and the stability of recorded magnetization deteriorates.
+2 The inconvenience of not being able to record occurs.

Therefore, in practice, it is required to optimize the characteristics of the amorphous perpendicularly magnetized film itself for the laser beam or recording/reproducing apparatus used. Therefore, the present inventors first confirmed that the Kerr rotation angle increases by replacing 1·e with CO even in the (Fet -xCOx)100-@DY'' ternary alloy for the m13 element system. By further substituting these rare earth elements, which are constituent elements of the above ternary system, with other rare earth elements, the Kerr rotation angle can be further increased, the figure of merit can be improved, and the coercive force can be used as a measure of the stability of the recording pit diameter. H
The product of C and saturation magnetization MS) (the product of c-MS) was attempted and completed in an attempt to obtain an amorphous perpendicular magnetization film having a Curie temperature suitable for practical use.In the quaternary alloy of the present invention, 1- The amount X by which 〇 is replaced with CO must be 0.1 (x≦0.4. Here, the effect of increasing the Kerr rotation angle due to co substitution becomes more pronounced (((=X is 0.1). It is preferable that it be larger than 1, and if x is larger than 0.4, the Curie temperature will increase to 230C or higher, making it difficult to write information with a semiconductor laser, so X needs to be 0.4 or less. Next, in the substitution of rare earth elements, in the Fe-C0-Dy system, part of I)y is replaced with Tb9 or Gd, and in the Fe-co-Tb system, part of Tb is replaced with Gd. Or by replacing with Dy,
In the Fe-Co-Gd system, part of Gd is replaced by Tb or Dy.
By replacing it with , it is possible to change the Curie temperature, make the figure of merit the same or higher, and greatly improve the recording/reproducing sensitivity. However, in order to obtain the effect of substitution between these rare earth elements, the amount of substitution must be 1,113.
It is desirable that the

Further, the value of a indicating the amount of the element in the 10th class is 17≦a≦32. 875F outside this range tends to inhibit the amorphization of the medium, which is not preferable.

[Embodiments of the invention] The implementation of this invention will be explained below with reference to FIG.

(Fex-bc oh)ysGdI9Tb6 amorphous film b
<0.4 is a J・1e Co alloy with a predetermined composition, G
A dTb alloy is produced in a vacuum high-frequency heating furnace, and using a Kameko beam evaporation device capable of two-step simultaneous evaporation, a
It was produced under the conditions of UT and film growth rate of 3 to 5A/5et3. Curve 1 in Figure 1 is (Fe1-bcob)7sG'ts
2 shows the change in the Kerr rotation angle θ with respect to the CO substitution amount of the Tbs amorphous alloy.

The figure shows (Ji'e1-bcob)rsTb2 for comparison.
The results for the 5 amorphous film are also shown in section 1112. As is clear from the figure, by replacing XTb with (d),
It can be seen that the Kerr rotation angle θk can be further increased.

On the other hand, the reflectance 几 remains almost unchanged over the entire composition range of the experimental results shown in Figure 1, showing 几=52 to 55%, so the figure of merit fπ・θ can be increased by replacing Tb with Qd. , improved playback output level can be obtained.

The curri temperature also varied in the range of 160 to 220C. By replacing Tb with J)y, it was possible to lower the Curie temperature and increase the recording and reproducing sensitivity without reducing the figure of merit ff·θk. Similarly, Fe-C
By replacing each rare earth element of o-Gd, , [i'e-Co-])y with another rare earth element, recording/reproducing characteristics superior to those of the ternary system were exhibited.

[Effects of invention]

As is clear from the above explanation, the quaternary amorphous #N, Fe-CoT ('l'=Gd, 'I'b
, D>'), it is possible to obtain a larger Kerr rotation angle θ of 1 and a figure of merit V1・θk than the conventionally reported amorphous perpendicularly magnetized film, which reduces the figure of merit. It is easy to optimize the temperature of cucumbers without
As a result, it was found that an excellent magneto-optical medium with good recording and reproducing sensitivity could be obtained.

It is clear that by using these amorphous films as constituent layers of a multilayer film medium, it is possible to further increase the Kerr rotation angle and improve the reproduced information level.

[Brief explanation of the drawing]

Figure 1 shows (Ii'el-bcOb)75Tb6Gd19
1(Fel-bCob)7s'l'l:+25 It is a diagram showing the dependence of CO exchange rate (b) on the Kerr rotation angle θ in an amorphous film.

Claims (1)

[Claims] 1. Select T from the group consisting of Gd, Tb, ])y2.
When used as an element, the general formula CF"1-zcOJloo-a
It has a composition shown by Ta≦, and 17≦a≦32.0
(A magneto-optical medium characterized in that x≦0.4.