JPS59116990A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent large variation of laser recording energy due to variation in characteristic of a recording medium when recording and to prevent large variation in magnetooptic effect and Faraday angle of rotation when reading by providing a magnetic film layer and a heat insulating reflection layer successively on a tansparent substrate. CONSTITUTION:The magnetic film layer 2 and insulating reflection layer 5 are provided on the sulestrate 1 and the reflection layer 5 combines a conventional insulating layer and reflection layer. When forming in a discoid shape, manufacture of the disk is easy if its film thickness is less than 3mm. in one side. A Tb- Fe magnetic film layer of film thickness 200Angstrom is provided on a glass substrate, and a TaN heat insulating reflection layer is manufactured by changing the film thickness. Even when recording is performed at 1MHz frequency by using semiconductor laser 900nm, the laser power does not change depending on the film thickness of TaN and the Faraday angle of rotation (thetaF) scarcely changes. CrN, AlN and MgN are used in place of TaN changing film thickness as a heat insulating reflection layer. Values of thetaF are 0.54 deg., 0.46 deg. and 0.68 deg. respectively, and the dependence on the film thickness was hardly recognized.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a rewritable magneto-optical recording medium having a novel layer structure. More specifically, the present invention relates to a magneto-optical recording medium having a heat insulating reflective layer.

Among various conventional optical memory devices, magneto-optical devices using various perpendicularly magnetized films as storage materials are attracting attention because they allow information to be rewritten.

However, this type of material has a low reproduction signal level, especially in the Kerr effect reproduction method, because the Kerr rotation angle is small, so the S/
It has drawbacks such as difficulty in increasing N. Therefore, in order to eliminate the above-mentioned drawbacks, it has been proposed to improve the magnetic material or provide a heat insulating layer such as SiO or 8102, or a reflective layer such as At (for example, JP-A-57-66
(See Publication No. 549). However, since the film is multilayered, the film fabrication is complicated and control is difficult. Another problem is that recording energy varies greatly depending on the thickness of the heat insulating layer, and absorption, reflection and heat insulating effects due to optical interference effects also vary greatly.

Purpose The present invention has been made in view of the above-mentioned problems, and one of its objects is to provide a magneto-optical recording medium in which the recording energy does not vary greatly due to changes in the characteristics of the recording medium when laser recording is performed on a magneto-optical recording medium. The goal is to provide the following.

Another object of the present invention is to provide a magneto-optical recording medium in which the magneto-optic effect and the Faraday rotation angle do not vary greatly due to variations in the characteristics of the recording medium when a recorded signal is read out from the recording medium using a laser beam.

Structure In order to achieve the above object, the present invention is characterized by using a heat insulating reflective layer that functions as both a heat insulating layer and a reflective layer.

That is, the magneto-optical recording medium of the present invention is one in which a magnetic film layer and a heat-insulating reflective layer are sequentially provided on a transparent substrate. If necessary, a protective layer may be provided on the heat insulating reflective layer.

The magnetic film thickness in the present invention is, for example, a transition metal (F
e, Go, N1, Mn, etc.) and rare earth metals (Ga, T
Magnetic alloy films obtained from various combinations, such as Tb-Fe
, ()d-Fe, Gd-Tb-Fe, Gd-Dy-
Fe, Tb-Fe-Co, Tb-Dy-Fe-Co
It is possible to use 1Gd-Tb-Fe-Co, etc.75 (possible).In this case, since the absorbance of these magnetic alloy films is large, the film thickness must be 5 ounces or less.

Further, an oxide magnetic material may be used, and a material having a low temperature is selected. Oxide magnetic materials generally have a high Curie temperature of 400° C. or higher, so the composition must be changed to lower the Curie temperature.

For example, BaFe12019 has a Curie temperature of 450°C.
BacotOTil, 0F10 because it cannot be used with more than
A method is used to lower the Curie temperature by replacing part of Fe with other atoms, as in o19. Further, the following oxide magnetic material can be used as the magnetic film layer of the present invention, but it is necessary to lower the Curie temperature by replacing a part of Fe with other atoms.

MeMzFe12-zO19, MeMxMyFe12
-(x+y)O19 or COMzFe2-ZO8 In each of the above formulas, Me is Ba, Sr, ! 3c, ,Pb
, Ca, etc., and Mx represents Co, Zn, At,
Cr, Mn, Ni, T1.3n, Cu.

pb, etc., and My is Co, At, Cr, Mn
, Ni, Ti.

Indicates Sn, Cu, Pb, etc. (MxNMy) and '1.' in M2. At, Zn, Cr, Mn,
Indicates Ni, 3n, Ti, pb, etc. Oxide magnetic material has better permeability than magnetic alloy film, and the film thickness is 600 to 100 mm.
It is within the range of X.

In addition, the heat insulating reflective layer in the present invention is made of a material having a thermal conductivity K of 100 (w/m, dθg) or less and a reflectance of 20 or more (for 800 nm laser light) when measured at 293°. Consisted of.

Examples of such materials include BN (K=11), ZrN (K
=14), 'I'aN (K= I O), Tln(x
=29), A2N, (K=15), MgN (3 in K
0), CrN (50 in K), HfN (20 in K),
Nitrides such as NbN (20% in K) can be mentioned.

EXAMPLE Hereinafter, an example according to the present invention will be explained in detail with reference to the drawings in comparison with an example of the prior art.

FIG. 1 is a schematic diagram showing the layer structure of a magneto-optical recording medium according to the prior art. , a heat insulating layer 3 (for example, 5i02), and a reflective layer 4 (for example, At) are formed by sequentially stacking them by sputtering, vapor deposition, etc., and are irradiated with laser light from the substrate side. In this case, the recording energy is greatly affected by the thickness of the heat insulating layer, and depending on the thickness, the absorption, reflection, and heat insulating effects due to optical interference effects become thicker (variable).Furthermore, the film fabrication is multi-layered and complicated, so it is difficult to control the recording energy. It is difficult to do so.

FIG. 2 is a schematic diagram showing the layer structure of the magneto-optical recording medium according to the present invention, and the provision of the magnetic film layer 2 on the substrate 1 is the same as shown in FIG. The difference is that the heat-insulating reflective layer 5 functions as both a conventional heat-insulating layer and a reflective layer, so that the thickness of the heat-insulating reflective layer, for example, when formed into a disk shape, can be up to 3 mm on one side. Since there are no restrictions, it is easy to manufacture a disk.

Effect Next, TaN is used as a material for the heat insulating reflective layer in the present invention.
The effect will be explained by taking as an example the case of using the method and comparing it with that of the prior art.

In contrast to the conventional technology, as shown in FIG.
A recording medium was prepared by providing a reflective layer of 5102 and varying the film thickness of the 5102 heat insulating layer, and recording was performed on the medium at a frequency of I MHz using a semiconductor laser (79 onm). The results are shown in FIG. In FIG. 3, the solid line shows the relationship between the film thickness and the energy (laser power) required for recording, and the dotted line shows the relationship between the film thickness and the Faraday rotation angle. It is clear from this that the laser recording energy varies greatly depending on the 5102 film thickness. ±10% variation in film thickness of 5102
is difficult to control, and the recording energy must be set at a high level.

On the other hand, in the recording medium of the present invention, as shown in FIG.
Even if the thickness of the N adiabatic reflective layer is varied and recorded using a semiconductor laser (900 nm) at a frequency of IMH2, the thickness of the N a The laser power does not change.The solid lines and dotted lines in FIG. 4 have the same meanings as in FIG. 3.

Furthermore, as shown in FIG. 3, in the conventional technology, the Faraday rotation angle (θF) changes significantly depending on the film thickness of 5i02, but this is due to the optical interference effect of the 5to2 layer and is a major problem. On the other hand, as shown in FIG. 4, in the present invention, the Faraday rotation angle (θF) hardly changes. Also, instead of TaN, Cr
When we prepared recording media with different film thicknesses using N, AtN, and MgN and investigated their characteristics, we found that θF
were 0.54°, 0.46°, and 0.68°, and there was almost no film thickness dependence.

Although TaN has been described above as an example for the sake of detailed explanation of the present invention, it goes without saying that similar results can be obtained with other materials.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the structure of a conventional magneto-optical recording medium, FIG. 2 is a schematic diagram showing the structure of a magneto-optical recording medium of the present invention, and FIGS. It is a graph showing the relationship between thickness, recording energy, and Faraday rotation angle. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Magnetic film layer, 3... Heat insulation layer, 4
... Reflective layer, 5... Heat insulating reflective layer.

Claims (1)

[Claims] A magneto-optical recording medium, characterized in that a magnetic film layer and a heat-insulating reflective layer are sequentially provided on a transparent substrate.