JPS63119049A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve C/N of a magneto-optical recording medium for which magnetoplumbite type ferrite layer is used by providing a layer of CoZn spinel ferrite layer adjacently to the magnetoplumbite type ferrite layer. CONSTITUTION:This recording medium is formed by laminating the CoZn spinel ferrite layer 13, the magnetoplumbite type ferrite layer 15 and a reflection layer 17 successively on a substrate 11 on which pregrooves are provided. The film thickness of the oxide magnetic material layer 15 is adequately about 0.1-1.0mum, more preferably 0.2-0.5mum. The CoZn spinel ferrite layer 13 is formed by various sputtering methods such as confronting target sputtering and magnetron sputtering. The film thickness of the CoZn spinel ferrite layer 13 is adequately about 0.05-0.5mum, more preferably 0.1-0.2mum. The magneto- optical recording medium having excellent C/N is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording medium using magnetoplumbite type ferrite.

BACKGROUND OF THE INVENTION In recent years, magneto-optical recording media have attracted attention in which information is recorded by writing magnetic domains in a magnetic thin film using the thermal effect of light and the like, and information is read out using the magneto-optic effect.

Currently, rare earth-transition metal amorphous alloys are being actively researched as magnetic materials used in magneto-optical recording media, such as GdCo and TbFe.

GdFaCo, TbFeCo, etc. are being considered. This amorphous magnetic material has no grain boundary noise, and the saturation magnetization Ms can be adjusted by changing the composition, so Ku>2
It has the advantage that a perpendicular magnetization film satisfying πMg'' (Ku: perpendicular magnetic anisotropy constant) can be obtained relatively easily.

However, since amorphous magnetic materials, particularly transition metal components, are susceptible to oxidative corrosion, there is a major drawback in that the magnetic properties of the magnetic film deteriorate over time. In order to prevent this, Si0. It is also known to provide a protective layer such as sio□, AQN, etc., but oxygen remaining in the vacuum during the formation of the magnetic layer or protective layer; oxygen or water adsorbed on the substrate surface; Oxygen, water, etc. contained in the magnetic film corrode the magnetic film over time, and the heat during recording further accelerates this oxidative corrosion. In addition, amorphous magnetic materials have the disadvantage that they are easily crystallized by heat, which tends to cause deterioration of their magnetic properties. moreover,
A 1 g A on the magnetic film to increase the reproduction output
u * A method in which a reflective film such as Cr is provided, a laser beam is irradiated onto the magnetic film, transmitted through it, reflected by the reflective film, and the reflected light is detected (reflection type Farade type) has a high C/N.
This is advantageous in that a ratio can be obtained. However, conventional amorphous magnetic materials lack light transmittance, so this method cannot be used.

Ba ferrite (
We have previously proposed a method using magnetoplumbite type ferrite, such as B.A.F. Since oxide magnetic material itself is an oxide, there is no risk of oxidation deterioration, and the film thickness can be reduced to 1
Since it has translucency even when it is 0μ or more, a one-reflection type Farade type can be adopted. Furthermore, it has been found that magnetic properties such as the Curie temperature and magneto-optical properties can be improved by adding various impurities.

However, taking Ba ferrite (B a F ez20zs), which is one of the magnetoplumbite type ferrites, as an example, Ba ferrite has a Faraday rotation angle of θp=o, 2deg/μ
Since the C/N ratio is not very large, it cannot be said that the C/N of a magneto-optical recording medium using Ba ferrite as a magnetic material is sufficient.

The same applies to other magnetoplumbite type ferrites.

m needle 1 season - The present invention aims to improve the C/N of a magneto-optical recording medium using magnetoplumite type ferrite which is excellent in terms of corrosion resistance and the like.

The magneto-optical recording medium of the present invention is a magneto-optical recording medium provided with a layer made of magnetoplumbite type ferrite.
C adjacent to the magnetoplumbite type ferrite layer.
It is characterized by providing a layer made of oZn spinel ferrite.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing an example of the structure of the magneto-optical recording medium of the present invention.
o A Zn spinel ferrite layer 13, a magnetoplumbite type ferrite layer 15, and a reflective layer 17 are laminated in this order. 19 indicates a protective layer.

The oxide magnetic layer 15 is made of magnetoplumbite type ferrite. Such oxide magnetic materials include ferrite represented by the following general formula and its Me or Fe
Examples include those in which part of is substituted with another element.

Meo・6Fe20. ”(1)(Me:B
a, Sr, Ca, Pb, La, etc.) The above-mentioned substitution elements include Go, Zn, Ni, A1, Ga
, Ti, Ta, etc., and these may be used alone or in combination of two or more.

The thickness of the oxide magnetic layer 15 is suitably about 0.1 to 1.0 μm, preferably 0.2 to 0.5 μm.

The oxide magnetic layer 15 can be formed by various types of sputtering such as facing target sputtering and magnetron sputtering, ion blasting, vacuum evaporation, plating, and other thin film forming methods.

The Co Zn spinel ferrite layer 13 is formed by various sputtering methods such as facing target sputtering and magnetron sputtering. C0Zn
The spinel ferrite layer 13 has a thickness of 0.05 to 0.5μ
The thickness is preferably about m, preferably 0.1 to 0.2μ.

Figures 4A and 4B show Ba ferrite and Co
Zn spinel ferrite (COL4ZnL+1F8
204), the θ, -H curve (λ = 780 nm) is shown.

Ba ferrite has Hc due to its large crystal magnetic anisotropy.
However, θF is not large enough.

On the other hand, CoZn spinel ferrite has a large perpendicular component due to induced magnetic anisotropy due to strain, but a stable perpendicular magnetization film cannot be obtained, and 02 in the perpendicular direction is large. In such a composite film in which two types of films with different properties are placed adjacent to each other, bits recorded on the magnetoplumbite type ferrite layer are transferred to the CoZn spinel ferrite layer by the stray magnetic field generated in this bit area. be done. Therefore, the Faraday rotation angle θa is the sum of θF of the magnetoplumbite type ferrite layer and θF of the CoZn spinel ferrite film, and becomes sufficiently large.

Further, since the saturation magnetization M8 and coercive force Ha of CoZn spinel ferrite decrease depending on the composition, transfer from a magnetized magnetoplumbite type ferrite layer is easily performed. Furthermore, as the amount of Zn increases, the Curie temperature decreases and the target composition N1IL, Zn,...,Fe
, O, then.

The temperature is 200°C, which is a suitable value.

However, considering that the larger the amount of Go, the larger θF, the CoZn spinel ferrite layer 13 is
Go□-@Zn, Fe, O, 0.3≦y≦0
．． 7 is preferred.

Furthermore, in the configuration example shown in FIG.

The CoZn spinel ferrite layer also functions as a base layer for the magnetoplumbite ferrite layer. Since the magnetoplumbite type ferrite film is oriented on the (111) plane of the spinel ferrite film so that the 0 plane is parallel to the substrate surface (hereinafter referred to as C-axis orientation),
By orienting CoZn spinel ferrite so that the (111) plane is parallel to the substrate surface (hereinafter referred to as (111) orientation), it can be used as a base layer for a magnetoplumbite type ferrite layer.

FIG. 5 is a graph showing the relationship between the (111) orientation of a CoZn spinel ferrite film produced by RF magnetron sputtering and the composition of the target material. The (111) orientation is expressed by fc shown below, and when fc=1, it means a completely (111) oriented film.

fc=P, H, (111)/ (P, H, (111)+
P, H, (311)) P, H, (111)...(11
1) X-ray diffraction peak height P, H, (311)-(3
11) Surface (7) X-ray diffraction peak height According to Figure 5, Zn
The larger the amount, the stronger the (111) orientation. Therefore, when CoZn spinel ferrite is used as the underlayer as in the configuration example shown in FIG. 1, the amount of Zn is increased, for example, Go, -1Zn, Fe12. 0.
It is preferable that 5≦δ. Therefore, the composition of the CoZn spinel ferrite layer needs to be determined while considering the magnetic properties and magneto-optical properties according to each layer configuration.

The reflective layer 17 is made of Au, An, Ag, Pt, Cr, Nd,
Rh, Cu, TiN, etc. are used, and electron beam (EB)
The film is formed by a thin film forming method such as a vapor deposition method.

The protective layer 19 is made of SiO, SiO, ZnS, ZnOlM.
gO, AQN, etc. are used and are formed by various sputtering methods such as magnetron sputtering and various vapor deposition methods such as EB vapor deposition.

The substrate 11 may be a metal material such as aluminum, aluminum-magnesium alloy, aluminum bronze, brass, chromel, stainless steel, or duralumin, or various glasses such as quartz glass, crystallized glass, Vycor glass, or Pyrex glass, or silicon, GGG, etc. , Li tantalate, AQ, 03, MgO1Boo.

Single crystals and sintered bodies of Zro, Y2O, The2, etc. are used. Note that when the light 10 is irradiated from the substrate 11 side as shown in FIG. 1, a transparent substrate is used.

As shown in FIG. 1, it is already known in the prior art that a large Faraday rotation angle can be obtained by utilizing the reflective Faraday effect in which the transmitted light from the magnetoplumbite ferrite layer 15 is reflected by the reflective layer 17. As explained in the column.

In this case, although it is already known, an even larger Faraday rotation angle can be obtained by providing an optical film 31 and utilizing multiple reflections, as shown in an example of the layer structure in FIG. The optical film 31 can be formed in the same manner as the protective film.

Of course, transmitted light may be directly detected without using a reflective layer.

FIG. 3 is a sectional view showing another example of the structure of the magneto-optical recording medium of the present invention. In this cross-sectional view, on the substrate ll,
Base layer 21, magnetoplumbite type ferrite layer 15
, CoZn spinel ferrite layers 13 are sequentially provided. In this configuration example, since the base layer 21 for C-axis orientation of the magnetoplant type ferrite is separately provided, the CoZn spinel ferrite layer does not need to be a (111) oriented film.
It is formed from etc.

According to the present invention, a magnetoplumbite type ferrite layer which becomes a stable perpendicular magnetization film with large crystal magnetic anisotropy;
By forming a composite film by adjoining a Co Zn spinel ferrite layer with a large vertical θF, a magneto-optical recording medium with excellent C/N can be obtained.

EXAMPLE A CoZn spinel ferrite layer (thickness: 0.2μ) having a composition of CoIL4Zn, Fe, O, was formed on a glass substrate, and furthermore, a layer of Ba
A F 8tzOzs film (thickness: 0.2 μm) was formed, and then a reflective layer made of Cr was formed to obtain a magneto-optical recording medium of the present invention.

On the other hand, a magneto-optical recording medium of a comparative example was obtained in the same manner as above except that a ZnO film was formed as the underlayer instead of the CoZn spinel ferrite layer.

For these recording media, semiconductor laser (wavelength 78
0nm), laser power 5IIw, medium speed 3
Recording was performed under the conditions of 1/see, and this was reproduced using the same semiconductor laser to determine the C/N.

-''1 (-m--Ω4 included U- Present invention product 52 It can be seen that the C/N is improved by using the magneto-optical recording medium of the present invention.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are cross-sectional views showing an example of the structure of the magneto-optical recording medium of the present invention. FIG. 4A is a graph showing the relationship between H and θF for Ba ferrite and FIG. 4B for CoZn spinel ferrite. FIG. 5 is a graph showing the relationship between target composition and (111) orientation. 11... Substrate 13... CoZn spinel ferrite layer 15... Magnetoplumbite type ferrite layer 17... Reflective layer Fig. 1 Fig. 2 Fig. 5

Claims (1)

[Claims] 1. A magneto-optical recording medium having a recording layer made of magnetoplumbite ferrite, characterized in that a layer made of CoZn spinel ferrite is provided adjacent to the magnetoplumbite ferrite layer.