JPH03296202A - Magnetic film - Google Patents

Abstract

PURPOSE:To obtain a transparent and chemically stable magnetic film having a perpendicular magnetic anisotropy, a large Faraday rotation angle and a magnetic property which can be changed freely to some extent by incorporating inside its columnar structure a substance which allows an easy transmission of light and a magnetic substance which shows a Faraday effect and has a low Curie temperature. CONSTITUTION:A magnetic film 2 formed on a substrate 1 is made of columns 3 and non-magnetic substance 4. Transparent substance and magnetic substance of which the column of the magnetic film is composed are particles of smaller diameter than that of the column and are joined lenghtwise. For the column, transparent substance and particulates of magnetic substance having a large Faraday rotation angle are used. The transparency and the Faraday rotation angle can be adjusted by changing the contents of the transparent substance and the magnetic substance. Substance which has a Curie temperature of 400 deg.C or below and which is good for opto-magnetic material includes TbFe. For the transparent substance, non-magnetic substance having no influence on the magnetism of the magnetic substance, such as Fe3O4, is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and particularly to a magneto-optical recording medium.

This recording medium relates to a magnetic recording method that performs recording and reproduction without using laser light, and a magnetic recording medium that is also used as a rewritable holography memory.

[Prior Art] Conventionally, magnetic films used in magneto-optical recording media, particularly magnetic films in which the plane of polarization of visible light rotates when light passes through the film, producing a magneto-optic effect (Faraday rotation), are made of Bi.
These include substituted iron garnet, MnB1, Ba ferrite, etc., and there are not many of them.

Conventionally, all of these magnetic films have been made of a single crystalline phase, and the crystal itself has good light transmittance. On the one hand, this means that the characteristics of the magnetic film are determined by the substance used in the magnetic film, and it is not possible to create a magnetic film with arbitrary characteristics.

Films with a large magneto-optical effect (Kerr effect) used in magneto-optical recording media, such as amorphous rare earth transition metal thin films such as TbFe and TbFeCo, have low transparency and were used by reflecting light on the surface of the film.

Needless to say, the magneto-optical recording medium must be a perpendicularly magnetized film.

Bulk Fe SCo SN i has a large Faraday rotation angle, but is opaque, an internally magnetized film, and has poor corrosion resistance.

Magneto-optical recording media that utilize the Kerr effect are not suitable for multiplex recording (multilayer recording) because they reflect light. Furthermore, the rotation angle is determined by the material used for the magnetic film.

On the other hand, when using the Faraday effect, if the light transmittance is improved, the rotation angle can be arbitrarily increased by increasing the film thickness (S/N is improved). Another advantage is that multiplex recording becomes possible.

As previously proposed (for example, Japanese Patent Application No. 1-135
No. 575), the columnar structure was made into a film composed of a material through which visible light passes (transparent material) and fine particles (several 10 to 500 particles) of a ferromagnetic material, such as Fe' or C01Ni. Because it is a fine particle, its transparency is much improved compared to bulk. or,
Fine particles of Fe5Co and Ni are connected vertically within the column.

Since the film is elongated vertically, shape anisotropy occurs, and magnetic anisotropy occurs perpendicular to the film surface, resulting in a perpendicularly magnetized film. In this case, there is no particular problem in the recording method on the film when a perpendicular magnetic head is used, but when it is used in a magneto-optical recording method in which recording is performed by heating the film with laser light, the following conditions are required.

That is, the temperature at which the magnetization of Fe, Co, and Ni disappears (Curie temperature) is the lowest for Ni, which is 358°C. Fe
,,co is higher than that, and a lower temperature is preferable for high-speed writing and erasing. In order not to disappear at room temperature, the temperature is preferably 1.50 to 250°C. However, when the above materials are heated, the coercive force decreases even in the case of Fe at, for example, about 350° C., and although it becomes easier to record, it is not sufficient because the square shape is not 1.

[Problems to be solved by the invention] The present invention has perpendicular magnetic anisotropy, is transparent, has a large Faraday rotation angle, is chemically stable, and has magnetic properties (perpendicular anisotropy, coercive force, etc.) The aim is to provide an artificial membrane that can be changed arbitrarily to some extent.

[Means for Solving the Problems] The configuration of the present invention for solving the above problems has a columnar structure in which the columns are separated by a non-magnetic material, and the inside of this columnar structure is transparent to visible light. This is a magnetic film containing a permeable substance and a magnetic substance that exhibits the Faraday effect and has a Curie temperature of 400° C. or lower.

To explain the structure of the magnetic film of the present invention in detail with reference to the drawings, a magnetic film 2 formed on a substrate 1 is composed of pillars 3 and a nonmagnetic material 4. As shown in FIG.

The thickness of the magnetic film 2 is preferably 500 to 5,000.

The diameter of the pillar is preferably 100 to 500 people, and the transparent material and magnetic material constituting the pillar are in the form of particles smaller than the diameter of the pillar and are arranged vertically.

Although the present invention uses a material with high light transmittance as a constituent component of the pillars, it is used as a magneto-optical recording material to improve recording sensitivity and facilitate erasing.

That is, instead of Fe, Co, and Ni, a material with a low Curie temperature (400° C. or less) is used (a material that performs compensation temperature recording and has a low recording temperature may also be used).

Furthermore, in order to provide the film with perpendicular magnetic anisotropy, the film was made to have a columnar structure separated by non-magnetic material.

By changing the diameter of the pillars, the magnetic properties of the film can be changed.

Next, a transparent material is used to construct this pillar. Next, fine particles of a magnetic material having a large Faraday rotation angle are used. Transparency and Faraday rotation angle can be adjusted by changing the content ratio of the transparent substance and the magnetic substance.

TbFe has a Curie temperature of 400°C or lower and is suitable as a magneto-optical material, including the following materials.

G d T b F e , M n A I G e
SM n Cu B i .

Examples include PtCo5TbDyFe and GdFeB1°TbCo.

Materials for compensating temperature recording include GdCo, GdFe, G
There are d I G (Gd iron garnet), etc. When these materials are formed into a thin film, they do not transmit light, but they are used as oxides or fluorides to improve transparency, or they are used in the form of fine particles.

Inside the columnar structure, outside the magnetic material, there is a carbon perpendicular to the film surface.
Inclusion of axially oriented ε-phase iron nitride improves perpendicular magnetic anisotropy.

ε-phase iron nitride has a h c p structure, with Fe):N(2<
X≦3), and it is considered that the perpendicular magnetic anisotropy is improved because the easy axis of magnetization is in the C-axis direction. The crystallite size of ε-phase iron nitride is 50 to 200 (X-ray diffraction method). Although the content is not particularly limited, it is preferably 50 wt% or less.

The transparent material is preferably a non-magnetic material that does not affect the magnetism of the magnetic material. Specific examples of this transparent material include oxides, nitrides, carbides, fluorides, etc., or amorphous materials thereof (including fine particle crystals), which envelop the magnetic material and improve corrosion resistance.

Transparent substances include the oxides, nitrides, and
Fluorides, carbides, etc., and oxides include Fe3O4
, Fe2O3, Fe01Co Os CO203, N
10% Nt 203 etc. However, even if it is not an oxide, it may have weak bonds such as those represented by Fe01Co-0 and Ni-0. Therefore, these amorphous substances may be used. Alternatively, the material may be in the form of fine particles that transmit light, but no diffraction peak is observed when examined by X-ray diffraction. In such cases, the light transmittance may be particularly high.

Substances exhibiting an hcp structure, such as ZnO1A I N, B e O, A 1203, T1, and Zr5Mg, are transparent and easily form a columnar structure.

As a nitride, Co 2 N SCO3N %Fe
4 N, F ex N (2<x≦3), N t
3N.

Fluorides include NlF2, FeF2, FeF3, CO
The F2, C0F3° carbide is Fe3 C5Fe2 C.

There is something like Fe5C2.

Some of these materials themselves tend to have a columnar structure, but when produced as a thin film, a columnar structure can be produced relatively easily. B that the columnar structure is due to the self-shading effect during film formation.
, A. MOVCllan and A.V.

Demchishin shows. It can be adjusted to some extent by gas pressure and substrate temperature. Mixtures of oxides, nitrides, fluorides, etc. may be used. In order to incorporate the magnetic material into fine particles in the film, N (nitrogen) is used in various thin film manufacturing methods.
This is possible depending on the composition ratio with O (oxygen) and film forming conditions.

In order to facilitate the formation of a columnar structure, the base layer may be prepared in advance. Further, a protective layer, a reflective layer, a lubricating layer, a dielectric layer, etc. may be provided on the magnetic layer as necessary. The magnetic layer and each of these layers are produced by a thin film forming method such as a vacuum evaporation method, an ion blasting method, a sputtering method, or a CVD method. Ion beam sputtering is preferred for producing the magnetic layer of the present invention.

The thickness of each layer is preferably 1 μm or less, and 0.05 to 0.05 μm.
Approximately 5 μm is appropriate.

Note that the fact that the transparency can be adjusted means that the absorption rate of laser light can be adjusted, making it useful as a magneto-optical recording medium.

As a support commonly used for magnetic recording media and magneto-optical recording media, appropriate non-magnetic materials such as plastic films, ceramics, metals, and glass are used. The plastics used here include not only heat-resistant plastics such as polyimide, polyamide, and polyenitersulfone, but also plastics such as polyethylene terephthalate, polyvinyl chloride, cellulose triacetate, polycarbonate, and polymethyl methacrylate. can. Further, the shape of the support may be any shape such as a sheet, a card, a disk, a drum, or a long tape.

The dielectric layer may include 5102, TlO2, silicon nitride, aluminum nitride, amorphous 81, etc., and the lubricant layer may include carbon layer, molybdenum dioxide, tungsten disulfide, α-olefin polymer, etc. Liquid unsaturated hydrocarbon (compound in which an n-olefin double bond is bonded to the terminal carbon; approximately 20 carbon atoms),
Fatty acids consisting of a monobasic fatty acid having 12 to 20 carbon atoms and a monohydric alcohol having 3 to 12 carbon atoms] Examples include stellates and the like.

The material for the reflective layer is Au5Al and Ag.

Pt, Cr5Nd, Ge, Rh, CuXTiN, etc. are used.

[Example code] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 A transparent magnetic film with a thickness of 4500× was produced on a disk-shaped glass substrate using an ion beam sputtering apparatus under the following conditions at a substrate rotation speed of 2 RPM.

Target material TbPe (Tb10wt%) Glass substrate temperature 100℃ Base pressure in vacuum chamber 8X 1O-7Torr Ionization gas Ar75%, N225% Ion gun voltage
9kV Ion gun current 2mA Ion incident angle 30°Introduced gas Oxygen] 1 Oxygen gas pressure 0.8X 10' Torr Distance between target substrates 17mm When the magnetic film produced under these conditions was examined by X-ray diffraction, a diffraction peak was found. I didn't.

When the cross section was examined using a TEM method, a columnar structure with a diameter of about 300 Å was observed.

When the composition of the film was examined by XPS, it was found to be Fe 47at%
, T b L2a1%, 038at%, N' 3at%
Met.

The light transmittance was 44% (λ=780 nm).

The magnetic properties examined by VSM were as follows for a perpendicularly magnetized film.

Hcl (coercive force) 4900eHo (coercive force) i300eMs (saturation magnetization)
350emu/ccSql (square ratio>
0.2] HK (perpendicular magnetic anisotropy field) 4.
7 kOe temperature (demagnetization temperature): 160° C. Next, while applying a maximum magnetic field of 12 KOe to this magnetic film, the Faraday rotation angle θ was measured using a semiconductor laser (wavelength: 780 nm). θF was 2.9cleg 2 7μm.

This measured value did not change even after two months after film formation.

Comparative Example A transparent magnetic film was produced in exactly the same manner as in Example 1 except that Fe was used as the target material.

When this magnetic film was examined by X-ray diffraction, only the diffraction peaks of the (002) and (004) planes of ε-phase iron nitride were observed.

When the cross section was examined using TEM, a columnar structure with a diameter of about 300 people was observed.

The light transmittance was 45% (λ=780 nm).

The magnetic properties examined by VSM were as follows for a perpendicularly magnetized film.

HC soil 420
0eHc 2200e M 5480emu/cc S, 10.29 HK 4.7KOe However, the Curie temperature (magnetization loss temperature) did not appear below 400°C.

θP measured in the same manner as in the example is 2.2 deg/μm
Met.

[Effects of the Invention] As explained above, the magnetic film of the present invention is a perpendicularly magnetized film having large perpendicular magnetic anisotropy and good chemical stability.
It is preferable as a magneto-optical recording material because its transparency, Faraday rotation angle, and magnetic properties can be adjusted arbitrarily to some extent, and each value is large. Of course, it can also be used in other recording methods, for example, as a perpendicularly magnetized film written with a perpendicular head.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of the magnetic film of the present invention. ■...Substrate, 2...Magnetic film, Pillar...4...Nonmagnetic material. 3 4

Claims (1)

[Claims] It has a columnar structure in which the columns are separated by a non-magnetic material, and the inside of this columnar structure is made of a material that easily transmits visible light, and
A magnetic film characterized by containing a magnetic material exhibiting a Faraday effect and having a Curie temperature of 400°C or less.