JPH0335512A - Manufacture of ce substituted garnet and optomagnetic recording medium - Google Patents

Abstract

PURPOSE:To freely vary magnetic characteristic compensating temperature of coercive force, aspect ratio, etc., by sputtering a film or heat treating after film forming in an inert gas atmosphere containing an oxidative gas or reducing gas in a method of manufacturing a specific Ce-substituted garnet. CONSTITUTION:In a method of manufacturing a Ce-substituted garnet represented by a formula (1), oxygen amount in the film is controlled to alter valance of Fe in the film. Or, the formed film is heat treated under suitable oxygen partial pressure. Since the valence of Fe is very sensitive to oxygen amount, fine oxygen amount control is required in this case. Large aspect ratio, coercive force, compensating temperature necessary as an optomagnetic recording medium are controlled in the garnet, and the characteristic is freely controlled by controlling the oxygen partial pressure at the time of sputtering, and controlling oxygen concentration at the time of heat treating after film forming.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method for producing a Ce-substituted garnet, particularly a method for producing a magneto-optical recording medium, and relates to a method for producing a Ce-substituted garnet, in particular, a method for producing a magneto-optical recording medium. The purpose of the present invention is to provide a method for controlling the magnetic properties of Ce-substituted garnet, which is formed by sputtering and is expressed by the following general formula (1). A manufacturing method in which the magnetic properties of the Ce-substituted garnet are controlled in an inert gas atmosphere containing a gas or an inert gas atmosphere containing a reducing gas;
The invention consists of a method for manufacturing a magneto-optical recording medium using e-substituted garnet, in which an oxygen-containing atmosphere is used during sputtering film formation of the Ce-substituted garnet or during heat treatment after film formation to control the amount of oxygen. do.

Cex R3-XMVF e5-. 012 HHH(1
) (0<x<3.o<y<s) [R is Y or a rare earth element other than Ce (ScLa, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho
, Er, Tm, Yb, Lu) M is Li which can be replaced with Fe.
, Mg, Zn, AlGa, Sc, In, Ti, Zr, H
f, St.

Ge, Sn, V, Nb, P, Cr
, Mn, Co.

Refers to an element selected from Ni. [Field of Industrial Application] The present invention relates to a sputtered garnet film used in magneto-optical recording media and the like.

[Conventional technology]

Bi substitution has conventionally been performed on sputtered garnet films for magneto-optical recording. When Bi substitution is performed, the Faraday rotation increases and the reading signal strength increases. However, the Faraday rotation of the Bi-substituted garnet film depends on the wavelength, and although it is very large in the visible light region, the value in the near-infrared region is not sufficient.

Usually, a semiconductor laser having an oscillation wavelength in the near infrared is used as a light source for an optical disk because it is compact. From this point of view, Bi-substituted garnet is not effective at semiconductor laser wavelengths.

Recently, CeN-modified garnets were found to have a large Faraday rotation in the near-infrared (e.g., M, Cyom
i, to, 5atoh and M.

Abe: Jap, Appl, Phys, 2
7. L1536 (1988), or the 12th Japanese Society of Applied Magnetics Academic Lecture Abstracts 2aA-4, 2aA-
5, 2aA-6 (1988)).

In these reports, epitaxial films and polycrystalline films are fabricated on single-crystal non-magnetic garnet substrates such as GGG or Si substrates, respectively, by sputtering. −
≦-1,7)Y3-XCexF e5-yA ly C
)+z(x-0,0,5,0,7,1,0,y=o,0
．． 8°1.2) is shown. In addition, Ce is usually tetravalent (
Ce'') is stable, and in order to obtain trivalent Ce (Ce''°), an inert gas Ar is used as the sputtering gas.

A film with the above composition has a very small squareness ratio and coercive force and cannot be used as a magneto-optical recording medium.

[Problems to be solved by the present invention]

The purpose is to provide CalCal negative net with magnetic properties suitable for magneto-optical recording. That is, a sufficiently large squareness ratio and coercive force are provided, and the Curie point, compensation temperature, and saturation magnetization, which are problems in the recording process, are controlled by film forming conditions and heat treatment conditions.

Faraday rotation increases when Ce is substituted, but the reason for this is not clear, but the fact that Ce is trivalent seems to be the key point. Therefore, despite the formation of oxides, the atmosphere during film formation must be reducing.

Normally, Fe in garnet is trivalent, but when produced in a reducing atmosphere or heat treated, oxygen vacancies occur in the film, and divalent Fe is generated to compensate for the charge. Since trivalent Fe and divalent Fe have different magnetic moments, their Curie temperatures and saturation magnetizations differ. Furthermore, in a garnet composition that has a compensation temperature, the compensation temperature also differs depending on the valence of Fe. Since the temperature dependence of saturation magnetization and coercive force varies greatly depending on where the compensation temperature is located, the position of the compensation temperature is particularly important in the recording process and bit stability.

From this viewpoint, the inventors changed the amount of oxygen when producing a Ce-substituted garnet film and found that the compensation temperature was very sensitive to the amount of oxygen.

[Means to solve the problem]

The present invention is formed by the following general formula (1) by sputtering method.
In the method for producing a Ce-substituted garnet represented by Ce
Manufacturing method of substituted garnet Ce X Ri-*MyF e 5-yo 12...
・(1) (0<x<3.Q<y<5) [R is Y or a rare earth element other than Ce (Sc).

La, Pr, Nd, Pm, Sm, Eu, Cd, Tb, D
y, Ho, Er, Tm, Yb, Lu) M can be replaced with Fe, Mg, Zn, AlGa, Sc, In, Ti,
Zr, Hf, Si.

Ge, Sn, V, Nb, P, Cr, Mn, Co.

refers to an element selected from Ni] and a method for manufacturing a magneto-optical recording medium using Ce-substituted garnet represented by the following general formula (1) formed by a sputtering method,
Method for manufacturing a magneto-optical recording medium that controls the amount of oxygen using an oxygen-containing atmosphere during sputtering film formation of Ce-substituted garnet or during heat treatment after film formation Ce++ RRx-3I, Fe, -yo+z H+
+ (1) (0<x<3.O<y<5) (R is Y or a rare earth element other than Ce (Sc.

La, Pr, Nd, Pm, Sm, Eu, Cd, Tb,
Dy, Ho, Er, Tm, Yb, Lu) M can be replaced with Fe, i, Mg, Zn, Al, Ga, Sc, In
, Ti, Zr, Hf, Si.

Ge, Sn, V, Nb, P, Cr, Mn　C.

Refers to an element selected from Ni. [Nimari] Intimidated.

That is, the present invention controls the amount of oxygen during film formation for the purpose of changing the valence of Fe in the film. Alternatively, the formed film is heat-treated under an appropriate oxygen partial pressure. Since the valence of Fe is very sensitive to the amount of oxygen, delicate control of the amount of oxygen is required at this time.

In Ce-substituted garnet, we can control the large squareness ratio, coercive force, and compensation temperature necessary for magneto-optical recording media, and freely change the above characteristics by controlling the oxygen partial pressure during evaporation and by controlling the oxygen during heat treatment after film formation. This is possible by controlling the concentration.

[Effect]

The magnetic properties of the film can be controlled according to the purpose. In particular, the compensation temperature can be changed significantly without changing the composition.

In amorphous rare earth transition metal alloys, which are currently mainly used as magneto-optical recording media, it is possible to control the compensation temperature below or above room temperature by changing the ratio of rare earth elements to transition metal elements. I can do it. Particularly in the case of a medium having a compensation temperature higher than room temperature, it is possible to erase only with a laser beam without an erasing magnetic field, which leads to direct override. In conventional garnet films for magneto-optical recording, the compensation temperature is below room temperature.

According to the present invention, even with a garnet medium, the compensation temperature can be made higher than room temperature, creating the possibility of direct override.

〔Example〕

Example 1 described below. In Example 2-, Ce1l
I! The converted garnet is formed into a film under the following conditions.

Ce and Ga-substituted DyIG films were prepared by RF2-pole Svanter as GOO (Gd2Gaso1z) and NGG (Nd
zGa50+z) was crystallized on a single crystal substrate (111) during film formation. During film formation, the temperature of the substrate is 6 to obtain a crystallized film.
The temperature was 75°C. The target is formally Ce D y
A powder target having a composition of zG ao, 3F 64.2012 was used. Powder target raw material oxide (C
e20x+ D yzOz+ Ga20 x + F
e 203) mixture in the atmosphere at 1000℃ for 2 to 3 hours.
The process of firing and pulverizing is repeated twice for press forming (16
t) A powder target of 75Φ×10 mm was prepared.

[Example 1] As a result of forming a film at 2 Pa using ArHz (1%) as a sputtering gas, the magnetic properties of the film significantly changed depending on the number of times the target was used (one sputtering time was about 1 hour including press sputtering). changed.

The sputtering conditions are shown in Table 1.

Table 1 Sputtering conditions target CeDy2Cyao, iFe4.
zO+z gas ArHz (1%) Gas pressure 2Pa Group (anti-N G G (
N d 3G ason 2) Group temperature 6 7 5 'CRF power density 5 X 10-"W/cm" Deposition rate 10
nm/min Deposited film thickness: approximately 0.3 μm Figures 1 and 3 are Faraday hysteresis loops of films produced for the second and fifth times, respectively, without replacing the target. (Substrate NGO measurement light wavelength 830n
m, film thickness approximately 0.3 μm), the sign of Faraday rotation is different, and the coercive force is also significantly different. Figures 2 and 4
The figures are Faraday rotation spectra for the same samples. The sign is reversed in a wide range from visible light to near-infrared light. The reason for this is thought to be that the target was reduced during multiple sputtering steps and the amount of oxygen on the surface changed.

In the case of Fig. 1 with a measurement light wavelength of 830 nm (film thickness a1on+
+) CeW substituted garnet DyzGao,s
Fea.

(2012), the Faraday rotation angle at zero magnetic field (reducing the magnetic field to O below which the Cei-substituted garnet is saturated) is 0.465 degrees, and the coercive force (HC) is 0.
It was 288 kilogauss. In addition, in the case of Fig. 3 (film thickness 3
00nm) Ce-substituted garnet (CeDyzG a
o, @F e a, zo +z) at zero magnetic field, the Faraday rotation angle is 0.304 degrees, and the coercive force (HC) is 1.
It was 778 kilogauss.

[Example 2] After press sputtering was performed for 2 hours or more by mixing oxygen as a sputtering gas, an atmosphere of Ar 0x (16%),
The film was formed at a gas pressure of 2 Pa.

The sputtering conditions are shown in Table 2.

Table 2 Sputtering conditions target Ce D y2c ao, l F
ea, z○Logas Ar-0□ (16%) Gas pressure 2Pa Base ヰAnti G G G
(G d 3G a 5012) Base Fi layer temperature 675'C RF power density 5 x 10-2 W/cm'' Deposition rate 10 nm/min Deposited film thickness Approximately 0.3 μm Figures 5 and 6 show the Faraday of the film. These are the hysteresis loop and the Faraday spectrum.The sign of the Faraday rotation is the same as in Figure 1, and it was confirmed that the change in sign is due to the difference in the amount of oxygen.

CeDyzGaa, a Fea, zO in Figures 5 and 6
The second sputtered film is a sputtered film deposited for the sixth time under the sputtering conditions shown in Table 2 without replacing the target. Even after multiple sputterings, the Faraday hysteresis loop and sign of Faraday rotation from the Faraday spectrum are the same as in the case of Figure 1 as described above, and depend on the number of sputterings as occurred with Ar-82 (1%). Therefore, the sign reversal of the Faraday rotation shown in FIGS. 3 and 4 does not occur, that is, when argon [Area (
16%)] is clearly effective.

In the case of Fig. 5 with a measurement light wavelength of 830 ns, Ce substituted garnet (Ce D YzG a (1, I F e4.s
on2) had a Faraday rotation angle of 0.094 degrees and a coercive force (HC) of 0.384 kilogauss.

In addition, in the above Example 1.2, the sputtering gas pressure was 2
Although the example using Pa was given, film formation was also possible at about 1 to 10 Pa. Further, although the substrate temperature differs depending on whether crystallization is performed during film formation or by heat treatment after film formation, a temperature of approximately 670° C. is required for crystallization during film formation.

[Example 3] Figures 7 and 8 show the results of investigating the temperature dependence of the Faraday hysteresis loop for the samples shown in Figures 1 and 3, respectively. In Figure 8, the compensation temperature is below room temperature. On the other hand, no compensation temperature is found in FIG. 7. In the case of FIG. 7, it can be seen that the compensation temperature virtually exceeds the Curie point. From this, it can be seen that the difference in the sign of Faraday rotation at room temperature is due to the difference in whether the compensation temperature is above room temperature or below room temperature. Normally, the compensation temperature (changes by changing the ratio of rare earth elements and iron elements), but the present invention takes advantage of the sudden changes caused by the difference in sputtering film forming conditions to adjust the coercive force, squareness ratio, compensation temperature, etc. It controls the magnetic properties of

As shown in Figure 5, Ar-16%0 is used as the sputtering gas.
Regarding the temperature dependence of the Faraday hysteresis loop of the sample of Example 2, which was sputtered at the 6th time using 2, almost the same results as those shown in FIG. 7 were obtained.

[Example 4] According to transmission electron microscopy FI (T-M) observation of the crystallized film during film formation on the NGG substrate or GGG substrate of Examples 1 and 2 above, it has a very smooth surface and a small crystal grain size. is about 10nm
It had a columnar structure.

ESCA analysis showed that the Fe and 0 peaks of the samples in FIGS. 1 and 3 obtained in Example 1 were different.

Figure 9 shows the peak of Fe by ESCA analysis, and the dotted line A
The solid line B corresponds to the sputtered film in FIG. 1, and the solid line B corresponds to the sputtered film in FIG. 3. The dotted line A corresponds to the sputtered film in FIG. The sputtered film has only two peaks (the peak or shoulder indicated by the arrow is observed in the dotted line A). Figure 10 shows the peak marked with ○ by ESCA analysis, and the dotted line A
The solid line B corresponds to the sputtered film in Figure 1, and the solid line B corresponds to the sputtered film in Figure 3.The dotted line A corresponds to the sputtered film in Figure 1, whereas the sputtered film in Figure 1 has a shoulder to the left of the peak as shown by the arrow. , the solid line B of the sputtered film in FIG. 3 has no shoulder to the left of the peak.

The structure of the magneto-optical recording medium is NGG substrate or GGG.
CeR3-XM was deposited on the substrate by sputtering as described above.
Fe, 3-, ○+zH may be formed, a vapor deposited A11l (approximately 0.1 μm) may be formed thereon as a reflective film, and recording and reproduction may be performed using an optical system using a semiconductor laser.

[Effects of the present invention] According to the present invention, by precisely controlling the oxygen partial pressure in the sputtering gas and the oxygen concentration during heat treatment, magnetic properties such as coercive force and squareness ratio necessary for magneto-optical recording and compensation temperature can be improved. It is possible to change freely.

[Brief explanation of drawings]

Figure 1 shows the Faraday hysteresis loop (wavelength 830 nm) of a sample fabricated using Ar-Hz as the sputtering gas and the same number of sputtering cycles. A diagram showing the spectrum of the Faraday rotation angle of the sample prepared in the eye (when the magnetic field is reduced to 0 from the negative magnetic field where the magnetization of the Ce-substituted garnet is saturated when the magnetic field is +0, the magnetization of the Ce-substituted garnet is saturated when the magnetic field is -0) Figure 3 shows the Faraday rotation angle at zero magnetic field when the magnetic field is reduced from a positive magnetic field to 0. Figure 4 is a diagram showing the spectrum of the Faraday rotation angle of a sample prepared after 5 sputtering cycles using ArHz as the sputtering gas. Figure 5 is a diagram showing the spectrum of the Faraday rotation angle of a sample prepared using ArHz as the sputtering gas and an oxygen amount of 16 nm. Figure 6 shows the Faraday hysteresis loop (wavelength 830 nm) of the sample prepared at the 6th sputtering time with % and the oxygen content was 16% using Ar-02 as the sputtering gas. Figure 7 is a diagram showing the temperature dependence of the coercive force of samples fabricated using ArHz (1%) as the sputtering gas and the same number of sputtering cycles. Figure 9 shows the peak of Fe by ESCA analysis. Figure 10 shows the peak of ○ by ESCA analysis. It is a diagram. 9I￥] +10 Figure Procedural Amendment (Method) Display of the Case 1999 Patent Application No. 170363 2゜Name of the Invention Relationship with the Case

Claims (2)

[Claims] (1) In the method for producing Ce-substituted garnet expressed by the following general formula (1) formed by sputtering, sputtering film formation or heat treatment after film formation is carried out in an inert gas atmosphere containing an oxidizing gas or a reducing gas atmosphere. A method for producing a Ce-substituted garnet, the method comprising controlling the magnetic properties of the Ce-substituted garnet in an inert gas atmosphere. Ce_xR_3_-_xM_yFe_5_-_yO_1
_2...(1) (0≦x≦3, 0≦y<5) R is Y or a rare earth element other than Ce (Sc, La, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho
, Er, Tm, Yb, Lu) M is Li which can be replaced with Fe
, Mg, Zn, Al, Ga, Sc, In, Ti, Zr,
Hr, Si, Ge, Sn, V, Nb, P, Cr, Mn,
Refers to an element selected from Co and Ni. (2) In a method for manufacturing a magneto-optical recording medium using a Ce-substituted garnet represented by the following general formula (1) formed by a sputtering method, oxygen is contained during sputter film formation of the Ce-substituted garnet or heat treatment after film formation. A method for manufacturing a magneto-optical recording medium, characterized by controlling the amount of oxygen using an atmosphere. Ce_xR_3_-_xM_yFe_5_-_yO_1
_2...(1) (0≦x≦3, 0≦y<5) R is Y or a rare earth element other than Ce (Sc, La, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho
, Er, Tm, Yb, Lu) M is Li which can be replaced with Fe
, Mg, Zn, Al, Ga, Sc, In, Ti, Zr,
Hf, Si, Ge, Sn, V, Nb, P, Cr, Mn,
Refers to an element selected from Co and Ni.