JPS6134744A - Photoelectromagnetic recording medium - Google Patents

Abstract

PURPOSE:To provide high coercive force and a large Kerr rotation angle and to optimize the Curie temp., corrosion resistance, etc. in accordance with uses by forming a vertically magnetized film contg. a larger amt. of iron-group elements in a rare earth-iron group medium of specified composition on an amorphous vertical magnetic film. CONSTITUTION:An amorphous vertical magnetic film, shown by the formula (R is >=1 kind selected from Gd, Tb, Dy, and Ho, T is >=1 kind selected from Nd, Eu, Er, Sm, Yb, Nb, Y, Al, and Ni, M is >=1 kind among Fe and Co, and x+y+ z=100, 5<=x<=14. 0 and 0<=y<=15), is formed on a Tb20Fe80 amorphous film formed on a nonmagnetic supporting body by electron-beam vapor deposition, etc. A film of (Tb0.95Gd0.05)13.(Fe0.95Co0.05) is especially formed by using >=2 kinds of R and 2 kinds of M, Fe and Co. Consequently, althought the concn. of rare earth elements is reduced as compared with the conventional recording medium, a photoelectromagnetic recording medium having a larger photoelectromagnetic effect than before and large signal reproduction output and S/N is obtained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to magneto-optical recording for recording, reproducing, and erasing information using laser light, and particularly relates to a signal-to-noise ratio S/ during reproduction.
The present invention relates to a magneto-optical recording medium having a large Kerr rotation angle and a large Faraday rotation angle, which is suitable for improving N.

[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 (perpendicular magnetization film) with an axis of easy magnetization perpendicular to the film surface is used, and by creating reversed magnetic domains at arbitrary positions with a light beam, the direction of magnetization can be adjusted. As a result, binary information of "1" and "0" is recorded.On the other hand, reading of the two types of signals after such inversion recording is normally performed using the Polar Kerr effect or the Faraday effect.

Conventionally, perpendicular magnetization films such as MnB1-based crystalline films, rare earth-transition metal-based amorphous thin films, and garnet single-crystal thin films have been proposed as these magneto-optical media.
Transition metal-based amorphous thin films are currently viewed as the most promising because they have no grain boundaries, have low media noise, and are easy to fabricate over large, homogeneous areas. Examples of these rare earth-transition metal-based amorphous thin films include those described in Japanese Patent Application Laid-Open No. 52-31703. Publication No. 57-34588.

JP-A-56-126907, JP-A-57-94948
, as shown in Japanese Patent Application Laid-Open No. 58-73746, etc., CO
In the system, Gd-Co, Gd-Tb-Co, and in the Fe system, T
b - F e .

Gd-Fe, Tb-Gd-Fe, Gd-Fe-Co, a
d-Dy-Tb-Fe, Dy-Fe-Co, Tb
-F e -G o , T b -D y -F
Alloy systems such as e-CO are currently being researched, and the Kerr rotation angle due to residual magnetization of the film itself has been improved to about 0.3''. The element concentration was limited to perpendicularly magnetized films of 15 to 35 atomic percent, which yielded relatively large values of the perpendicular magnetic anisotropy energy, Ku.

However, in order to obtain a reproduced signal level for practical use, the Kerr rotation angle or Faraday rotation angle obtained with these conventional alloy systems is insufficient, and the magneto-optical effect of the film itself is required to improve the S/N ratio. Improvement is required.

[Purpose of the invention]

An object of the present invention is to obtain a sufficiently large magneto-optic effect and a high reproduction S/N ratio (or C/N ratio).

The object of the present invention is to provide an amorphous magneto-optical recording medium that is most suitable for practical use.

[Summary of the invention]

The structure of the present invention for achieving the above object is that one compositional formula is R.
It is represented by xTyMz, and the above R is Gd and Tb.

At least one element selected from the elements consisting of Dy and Ho, the above T is NdtEu, EtzSm, Yb,
At least one element selected from the group of elements consisting of Nb, Y, Al, and Ni, where M consists of at least one element selected from the group of elements consisting of Fe and Co, and in atomic percent, x + y + z = 1
00, 5≦x<1.4.0<y<15, and is preferentially amorphous.

Rare earth-iron group amorphous films, which are attracting attention as candidate materials for magneto-optical materials, have conventionally had a rare earth element concentration of 15 to 35 atomic percent (for example, in JP-A-56
-126907), magnetization was perpendicular to the film surface in this composition range, and a relatively large Kerr rotation angle was obtained. However, within these composition ranges, as the iron group element concentration increases beyond the compensation composition, the saturation magnetization Ms increases, and therefore 2πMs
Since the magnetostatic energy increases due to the demagnetizing field shown by 2,
The direction of magnetization gradually changes from the perpendicular direction to the in-plane direction. As a result, the magnetochemical effect due to residual magnetization is reduced, so it was thought to be unsuitable for magneto-optical recording films that require high magneto-optic effects.

However, the present inventors have investigated the Faraday rotation angle of amorphous thin films rich in rare earth-iron group elements under an external magnetic field of 20 kG applied perpendicular to the film surface. 0. When measuring θ, it was found that θ increases as the iron group element concentration increases, and that a high magneto-two-optic effect can be obtained especially at the high concentration side where iron group elements are rich. However, as the concentration of iron group elements increases, the coercive force decreases, and in compositions rich in iron group elements that yield high Ol, the coercive force is generally 1000e.
This has the disadvantage that recording cannot be performed stably because the size of the recording medium is smaller than that.

On the other hand, as a method for increasing the magneto-optic effect, Katayama et al. recently reported that a perpendicularly magnetized film with a Kerr rotation angle larger than Tb - F C is formed on a Tb, □Fe, Gd1. J
Co, I, or Gd7Tb, , Co41Fe, , R
By coating with an amorphous film, the apparent T b −F
Attempts are being made to increase the Kerr rotation angle of
．． 11) P, 233).

Based on these findings, the present inventor first developed Tb--Fe or T b
-Fe with a large magneto-optic effect is placed on the Co perpendicularly magnetized film.
Alternatively, a Co metal film is coated to a thickness of approximately 40 to 60 nm, and the exchange interaction with the perpendicular magnetization film allows Fe or Co
An attempt was made to obtain a magneto-optical recording medium with a large magneto-optic effect by orienting the magnetization direction of the o-film perpendicular to the film surface. However, because the saturation magnetization of Fe or Co is too large, 21 kG or 18 kG, respectively, the direction of magnetization of these films is not perpendicular to the film surface due to exchange interaction.
On the contrary, it has the effect of directing the magnetization direction of the underlying Tb-Fe or Tb-Co film from the perpendicular direction to the in-plane direction,
As a result, it was found that the magneto-optic effect as a medium deteriorates.

Therefore, the present inventors developed the above-mentioned rare earth-iron group amorphous thin film rich in iron group element concentration, which has a relatively low saturation magnetization and a large magneto-optical effect, on an amorphous perpendicularly magnetized film. When coated with the medium, a high coercive force of 1 k Oe or more was obtained, and the Kerr rotation angle at residual magnetization was 0.2 to 0.35 degrees compared to the conventional amorphous perpendicularly magnetized film COv. It was found that a high Kerr rotation angle value (0.35 degrees or more) which could not be obtained with ) was obtained, making it suitable as a magneto-optical material.

In the magneto-optical recording medium of the present invention, substantially R is Gd, Tb
, Dyt, Ho, and T is Nd or Eu.

at least one element selected from the group of elements consisting of Er, Sm, Yb, Nb, Y, Al, and Ni; M is Fe;
A rare earth-iron group amorphous material consisting of at least one element selected from the element group consisting of Co, having the general formula Rx T y M z, and having a total concentration of rare earth elements R of 14 atomic percent or less. It is a membrane.

Here, in the alloy film of the present invention, in order to obtain a larger magneto-optical effect than the conventional rare earth-iron group amorphous film, it is preferable that the rare earth element concentration is 14 atomic percent or less, but 5M atomic percent or less. Since it becomes difficult to make the material amorphous, the rare earth element concentration needs to be 5 atomic percent or more. If necessary, some of the constituent elements Fe or Co may be replaced with Nd+Eu, Er, Sm, Yb* in order to adjust the recording/playback sensitivity.
Nb, Y, AM.

By substituting 15 atomic percent or less with elements such as Ni, the performance as a magneto-optical recording medium can be optimized.

Furthermore, an amorphous film can be formed by using at least two of the constituent elements of the present invention, ad, Tb, and Dy+Ho, as vitrifying elements (rare earth elements play this role in rare earth-iron group amorphous films). Therefore, magneto-optical effects such as the Curie temperature, Faraday rotation angle, Kerr rotation angle, etc. can be enhanced more than in the case where the rare earth element is an amorphous film.

Fct again! : By replacing CO with Fe or by replacing CO with Fe, the magnitude of magnetization of iron group elements that contribute to the magneto-optical effect is increased, and further, rare earth elements that are other constituent elements are replaced with other types of rare earth elements. By doing so, the magneto-optical effect can be further improved, the Curie temperature can be optimized at the same time, and the recording sensitivity and reproduction output can be greatly improved.

In the above rare earth-iron group amorphous film of the present invention, B, Si
By adding 10 atomic percent or less of nonmetallic elements such as or transition metal elements other than the constituent elements of the present invention, the magnetic properties, Curie temperature, crystallization temperature, corrosion resistance, etc. of the film properties can be further optimized depending on the application. You can also do that.

[Embodiments of the invention]

The present invention will be explained below using examples.

The amorphous alloy film of the present invention has a diameter of 110 mm and is made of CO or F.
By sputtering 5×5+nm2 of rare earth elements or reduced metal elements onto the e-disc-H using a composite target arranged to have a predetermined composition in terms of area ratio, or by vacuum arc melting to create an alloy with a predetermined composition. They were fabricated by electron beam evaporation using these master alloys.

An embodiment of the present invention will be explained with reference to FIG. Tb, Co, -, + (Tb-q+; Gd-ns
)-COX-1(Tb, g<Gd, as)-(Co,
psFe, ns) The 1-a amorphous film (as20) was prepared by magnetron sputtering at an Ar pressure of 5X 10-3 Torr.
, under conditions of input high-frequency power of 1 kW, or under conditions of vacuum degree I x 10-' Torr in the case of electron beam evaporation. The thickness of the produced amorphous film was kept constant at about 500. The film produced under such production conditions had a of 5 atomic percent (I3t, %) or more and was amorphous. Figure 1 shows Tb, Co, -. (Shiraito!l) +
(Tb, qqGd, 5) ecOl-a
(Curve 2) + ('I'b-3sGd-as)
−(Co, g5Fe, os) +−(Curve 3) Faraday rotation angle θ of amorphous film, etc., (measurement wavelength λ = 633 n
m ) is expressed as a function of rare earth element concentration a and 1 no. From the diagram, the constituent elements of rare earth elements are determined from 1゛b to T.
)) It can be seen that θ is increased by changing the -G d to binary, or by changing the constituent elements from CO to Co--Fe in the case of iron group elements. It can also be seen that as the rare earth element concentration decreases, that is, as the iron group element concentration increases, θ increases, and a large value of 0 is obtained when a<15 at%. Similar trends were observed in rare earth-iron group amorphous films rich in Fe elements.

Next, we will discuss Tb2 n Fe, a typical perpendicular magnetization film of conventional materials.
1l.

On the amorphous film (thickness: about 1,000 layers), coat the amorphous film of the present invention with a large magneto-optic effect without breaking the vacuum by about 50 layers, and then coat the L with Sin, and coat the film by about 1,000 layers. Multilayer media were prepared, and their Kerr rotation angles from the Sj 02 side (measurement wavelength λ = 633 nm) were measured. As a result, Tb of the conventional material. F4. . 0 for the case of amorphous alone. (=0.2.2~0.25°), it was found that the increase was approximately 15.5°.

For example, Tb. When Tb14Fe, +6 amorphous aluminum is coated on Fe, lo, it is 0, = 0.28 to 0.30°.

(Tb, i<Gd, ns) 0 when coated with 1.0co'll amorphous film, = 0.33~0.386° (Tb, 5sGd, ns) +3 (Fe, ggco, n
s) +17 When coated with an amorphous film, it is 0. =0.30~
0642°1, and the coercive force HC of these multilayer films was as large as 1 to 2 kOc, indicating that they are suitable as magneto-optical materials.6 [Effects of the Invention] As is clear from the above description, the present invention The amorphous film with a low concentration of rare earth elements of the invention exhibits a larger magneto-optic effect than conventionally reported magneto-optical amorphous films, and has the advantage of providing a larger signal reproduction output to noise ratio (S/N). It turned out to be a magneto-optical recording material. In addition, since rare earth elements are expensive in rare earth-iron group amorphous films, the amorphous film with a low concentration of rare earth elements of the present invention has a lower concentration than conventional amorphous films.
Figure 1 shows TbaCox-at (Tb, 1
．． ,Gd,. ), Co□-1゜(Tb, qsGd, n
,,)-(CO,5sFe,os)1-h It is a diagram showing the a concentration dependence of the Faraday rotation angle θ in an amorphous film.

1-4b, Co1-, . 2- (Tb, 5sGd-n+
;) -COt-, 3...Figure 1

Claims (1)

[Claims] 1. The compositional formula is represented by RxTyMz, and the above R is Gd, T
b, at least one element selected from the elements consisting of Dy, Ho, and the above T is Nd, Eu, Er, Sm, Yb
, at least one element selected from the group of elements consisting of Nb, Y, Al, and Ni, where M consists of at least one element selected from the group of elements consisting of Fe, Co, and in atomic percent, x+y+z =100, 5≦x
A magneto-optical recording medium that satisfies <14, 0<y<15 and is predominantly amorphous. 2. In claim 1, the above R is Gd.
, Tb, Dy, and Ho. 3. In claim 1, the above M is Fe.
A magneto-optical recording medium comprising two elements: and Co. 4. In claim 1, the above R is Gd.
, Tb, Dy, and Ho, and wherein M is composed of two elements, Fe and Co.