JPH04345940A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To suppress the deterioration in recording and reproducing characteristics by the influence of the diamagnetic field and magnetic wall energy from the non-recording parts between recording tracks by setting one or both of the vertical magnetic anisotropy and exchange bonding strength of the magnetic recording films in the non-recording parts smaller than the values in track parts. CONSTITUTION:Polycarbonate, polymethyl methacrylate, epoxy resin, glass, etc., are used as a substrate and the vertical magnetized films of amorphous films or single crystal films consisting of TbFeCo, GdTbFe, DyFeCo, etc., are used for the magnetic recording layers. Films which are large in both of the vertical magnetic anisotropy and exchange bonding strength as the magnetic characteristics of the recording layer are used. Namely, the films having vertical magnetic anisotropy constant Ku>10erg/cm<2> and exchange constant A>10<-7> erg/cm are used. The values of either or both of the constants Ku and A of the non-recording parts between the recording parts are set smaller than the values of the recording tracks at this time. For example, the constant Ku is set at $ 50% of the value of the track parts and the constant A is set at <=50% as well.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable magneto-optical recording medium.

0002

[Prior Art and Problems to be Solved by the Invention] Various types of magneto-optical recording systems have been proposed up to now.
When recording magnetic domains are formed in a conventional magneto-optical recording medium using the magnetic field modulation method described in Publication No. When recording, the spot diameter of the irradiation light, pulse width, irradiation power, single pulse or continuous pulse are used when switching the direction of magnetization to be recorded from downward to upward or upward to downward with respect to the medium surface. When recording using a method in which signals are recorded by changing the method of irradiation of light such as at other times, the recording track (
The shape of the recorded magnetic domain is affected by the demagnetizing field from 1) in Figure 1 and the non-recording area between the recording tracks (2 in Figure 1), or the domain wall energy generated between the recording track 1 and the non-recording area 2. There was a problem that this led to a decrease in C/N or an increase in jitter during playback (IEE of Japan Magnetics Study Group Materials, MAG-87-178, 19861).
(October 28th, etc.)

On the other hand, in the system using an exchange-coupled two-layer film described in Japanese Patent Laid-Open No. 62-175948, etc., the stability of recording in the presence of an interfacial domain wall is seen as a problem. That is, as shown in FIG.
' together with the recording magnetic domain, which has a negative effect on the stability of recording. In the figure, 3 is a magnetic recording layer, 4 is a recording layer, and 5 is a recording auxiliary layer.

The present invention has been made to solve the problems of the prior art, and when the above magnetic field modulation method or the method described in Japanese Patent Application No. 2-64959 is applied. In order to improve the shape of the recorded magnetic domain, improve the reproduction C/N and reduce jitter, on the other hand, when the method using the exchanged two-layer film as described above is applied, it is necessary to stabilize the recorded magnetic domain. An object of the present invention is to provide a magneto-optical recording medium that can improve performance.

[0005]

[Means for Solving the Problems] In order to achieve the above object, according to the present invention, a magnetic recording film having perpendicular magnetic anisotropy is provided on a substrate, and a non-recording film is provided between tracks on which information is to be recorded. In the magneto-optical recording medium having a section, the perpendicular magnetic anisotropy and/or exchange coupling force of the non-recording section are set to be smaller than the perpendicular magnetic anisotropy and/or exchange coupling force of the adjacent track. A magneto-optical recording medium is provided.

The magneto-optical recording medium of the present invention will be described in detail below. The magneto-optical recording medium of the present invention basically has a structure in which a magnetic recording layer is provided on the side of the substrate on which pregrooves, wobble pits, etc. are formed, but if necessary, a protective layer, a reflective layer, etc. , an intermediate layer, an adhesive layer, a protective substrate, etc. may be formed. Alternatively, it may be of a double-sided bonding type.

The substrate is made of polycarbonate, polymethyl methacrylate, epoxy resin, glass, glass coated with UV resin, etc., and has pregrooves, wobble pits, etc. formed on the surface to limit recording tracks. is used.

[0008] The magnetic recording layer is an amorphous film or a perpendicularly magnetized single crystal film, and may be a single layer or a laminated film. Rare earth-transition metal (RE-TM) amorphous alloy films are mainly used. A typical example is TbF
Examples include eCo, GdTbFe, DyFeCo, and the like. The inherent magnetic properties of the magnetic recording layer include large perpendicular magnetic anisotropy and exchange coupling force (perpendicular magnetic anisotropy constant Ku
>106 erg/cm3, exchange constant A>10-7er
g/cm), but the present invention is characterized in that the value of either or both of the perpendicular magnetic anisotropy constant and exchange constant of the non-recorded area between the recording tracks is smaller than the value of the recording track. . The perpendicular magnetic anisotropy constant of the non-recording portion is suitably 50% or less of the value of the recording track portion. In addition, the exchange constant of the non-recording area is less than 50% of the recording track area.
The degree is appropriate. Since the non-recording area is not directly involved in recording, even if these values are small, there is no particular adverse effect on the recording and reproducing characteristics of the magneto-optical recording medium.

Next, an example of a method for manufacturing a magneto-optical recording medium having a magnetic recording layer having the above characteristics will be described. The first method is to create a magnetic recording layer in the non-recording area by irradiating the non-recording area with a laser beam that is higher in output than in general optical recording, using the same method as for general optical recording, after producing the magnetic recording layer. This is a method of changing the magnetic properties by giving some kind of structural change to the material.

The second method is to change the magnetic properties by selectively irradiating the non-recording area with charged particles or high-speed neutral particles after forming the magnetic recording layer and before forming the protective layer. As a specific example, an ion beam is obliquely irradiated onto a medium with pregrooves in a vacuum as shown in FIG. If the width to depth ratio of the groove is about 10:1,
If the light is incident at an angle of about 100 degrees, it becomes possible to selectively irradiate only the land portions. Non-magnetic metal ions are particularly effective as the type of ions to be irradiated.

[0011]

According to the present invention, since the perpendicular magnetic anisotropy and/or exchange coupling force of the non-recording portion of the magnetic recording layer is set to be smaller than the value of the track portion, the reaction from the non-recording portion is reduced. The magnitude of the magnetic field and the domain wall energy of the domain wall generated between the recording track and the non-recording portion become smaller (if the non-recording portion becomes completely non-magnetic, these values become 0). Therefore, the above-mentioned magnetic field modulation method or Japanese Patent Application No. 2-64
When the method described in the '959 specification is applied, the shape of the recorded bits is improved, the C/N ratio is improved, and jitter is reduced. Furthermore, when applied to a system using an exchange-coupled two-layer film type magneto-optical recording medium, recording bit stability is improved and reliability is improved.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing recording tracks, non-recording areas, and recording magnetic domains formed in the recording tracks of a magneto-optical recording medium.

FIG. 2 is a perspective cross-sectional view showing a recording magnetic domain formed in a magneto-optical recording medium of an exchange-coupled two-layer film type.

FIGS. 3(a) and 3(b) are diagrams each showing a method for reducing perpendicular magnetic anisotropy or exchange coupling force in a non-recording area.

[Explanation of symbols]

1 Recording track
2 Non-recording part 3 Magnetic recording layer
4 Recording layer 5
Recording auxiliary layer
6 Domain wall 6' interface domain wall
7 Substrate 8 Protective layer
9
ion beam

Claims (1)

[Claims] 1. A magneto-optical recording medium comprising a magnetic recording film having perpendicular magnetic anisotropy on a substrate and having a non-recording area between tracks on which information is to be recorded, wherein the perpendicular magnetic anisotropy of the non-recording area is 1. A magneto-optical recording medium characterized in that the orthotropy and/or exchange coupling force are set to be smaller than the perpendicular magnetic anisotropy and/or exchange coupling force of adjacent track portions.