JPH03162737A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve coercive force for high-density recording by alternately repeatedly laminating single metal layers of platinum group element and alloy layers of iron group elements and platinum group element. CONSTITUTION:On a substrate 1 comprising transparent material such as glass, there are alternately laminated layers of Co layer 2 having 5 Angstrom thickness and Pt-Pd alloy layer 3 having 25 Angstrom thickness. These layers are repeatedly laminated in this order to the end layer of Pt-Pd alloy 3 on the opposite side to the substrate so as to obtain 300 Angstrom total thickness. Thereby, the coercive force of the medium becomes as high as 750 Oe, which enables high-density recording and stable storage state.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magneto-optical recording medium on which information can be written. [Prior Art] Generally, this type of magneto-optical recording medium is constructed by applying a magnetic field in a fixed direction and depositing a film of magneto-optical recording material on a glass substrate surface with the direction of magnetization aligned. For reproduction, a laser beam spot is irradiated onto the film surface to heat it, and the direction of magnetization in that area is reversed by the surrounding magnetic field. For reproduction, a linearly polarized laser beam spot is irradiated onto the recording surface, causing a deformation of the recording surface. This is done by detecting the rotation of the polarization plane of the reflected light as a change in light intensity through an analyzer.

In this type of magneto-optical recording medium, preventing oxidation of the material is an important issue in maintaining its magneto-optical recording characteristics. A structure in which platinum (Pt) layers and cobalt (Co) layers are alternately stacked on a glass substrate is known (Journal Applied
Physics Vol-63, No. 10+15
May 1988 pp. 5069-5070).

Coercive force is an important characteristic of magneto-optical recording media. If the coercive force is small, it will be easily affected by external magnetic fields, leading to inconveniences such as erasure of recorded data, requiring strict storage, and cannot be said to have sufficient characteristics as a magneto-optical recording medium. .

[Problem to be solved by the invention]

By the way, it is known that the coercive force of a magneto-optical recording medium changes when the lamination period of the metal layers that make up the laminated film changes. The coercive force of a magneto-optical recording medium that has laminated films that are alternately stacked so that the total film thickness is 100 people per period is 1.
600e, and the nickel (Ni) layer and pt
In the case of a magneto-optical recording medium having a laminated film in which layers are alternately laminated, the thickness is about several 100 e, and the total film thickness is 700 e with a period of 17 layers for the PT layer and 6 layers for the Co layer. In the case of a magneto-optical recording medium with a laminated film that has the highest coercive force, the upper limit is about 4000e, which has the disadvantage that the coercive force is weaker than the lkoe required to maintain recording safety. .

The present inventors conducted various experiments and research to increase the coercive force, and as a result, they discovered that the coercive force can be improved by combining a single metal layer and an alloy layer, or a combination of alloy layers.

The present invention was made based on this knowledge, and its purpose is to provide a magneto-optical recording medium that has a high coercive force and is capable of high-density recording. [Means for Solving the Problems] The magneto-optical recording medium according to the present invention comprises a layer of a single metal of a platinum group element and an alloy layer of a metal of an iron group element and a metal of a platinum group element, alternately formed multiple times. It is characterized by having laminated films.

[Effect]

According to the present invention, the coercive force can be improved to approximately twice that of conventional products.

〔Example〕

The present invention will be specifically explained below based on drawings showing embodiments thereof. FIG. 1 is a cross-sectional structural diagram of a magneto-optical recording medium according to the present invention, and numeral 1 in the figure indicates a substrate formed using a transparent material such as glass. On the board 1 is a 5-piece thick plate (
Co) layer 2 and a thickness of 25 layers of flatiner palladium (
Pt-Pd) alloy layer 3 is repeatedly laminated in this order,
The final layer on the side opposite to the substrate 1 is a PL-Pd alloy layer 3, and the overall film thickness is set to 300 layers.

The composition ratio of pt and Pd in the Pt-Pd alloy layer 3 is 1
:Iatomic%.

In addition, although the above-mentioned example explained the structure which combined Co layer 2 and Pt-Pd alloy layer 3, it is not limited to this, for example, the structure which laminated Co-Pd alloy layer and pt layer alternately, i.e. A structure in which alloy layers of iron group metals and platinum group metals and single platinum group metal layers are alternately laminated, or a structure in which Co-Pd alloy layers and ptPd alloy layers are alternately laminated. In other words, it may be a structure in which alloy layers of iron group metals and platinum group metals and alloy layers of platinum group metals are alternately laminated. FIG. 2 is a schematic diagram of a high frequency sputtering device used for forming the Co layer 2 and the Pt--Pd alloy layer 3, and 11 in the figure indicates a vacuum chamber. In the lower part of the vacuum chamber 11, a Co target I2, a pt target l3, and the p target are placed across a partition wall 11a.
Pd targets l4 are arranged so as to occupy approximately 50% of the surface area of the target I3, and the vacuum chamber 11
A disk-shaped substrate holder 15 is horizontally rotatably disposed at the center of the upper wall of the substrate holder 15, and the substrate 1 is mounted on the lower surface of the substrate holder 15. and the shaft 15 of the substrate holder 15
a and the target 2 and the target}13. 1
A high frequency power supply I6 is connected between each of the two terminals 4 and 4.

Therefore, in such a sputtering apparatus, a vacuum chamber
After setting the inside to a predetermined degree of vacuum, the substrate I is placed in the substrate holder 1.
The target 12.5 is fixed to the lower surface of the target 12. 13. 14, the voltage of the power supply l6 is applied between the targets 12, 13. Sputter 14,
The sputtered material is directed to the surface of the substrate l and deposited thereon. Since the substrate holder I5 is rotating, the substrate 1
When it comes to the area facing the Go target l2 partitioned by the partition wall 11a, the Co layer 2, then the Pt, Pd target 13. When you come to the area facing 14, Pt
, alloy layers 3 containing Pd at a predetermined ratio are laminated on the surface of the substrate 1, and as the substrate holder 15 rotates, the Co layer 2 and the Pt--Pd alloy layer 3 are alternately laminated one after another. I will continue to do so.

Figure 3 shows the Kerr hysteresis loop for a product of the present invention in which Pt-Pd alloy layers 3 and Go layers 2 are alternately laminated, and Figure 4 shows the Kerr hysteresis loop for a conventional product in which PT layers and Co layers are alternately laminated. These are graphs showing the applied magnetic field (kO
e), and the Kerr rotation angle (deg) is plotted on the vertical axis.

As is clear from this graph, the squareness ratio of both the inventive product and the conventional product is approximately lOO%, but the coercive force of the conventional product is 400%.
0e, whereas the coercive force of the product of the present invention is 750 0e.
It can be seen that this has increased significantly. [Effect] As described above, the product of the present invention has a structure in which a simple metal layer of a platinum group element and an alloy layer of an iron group metal and a platinum group metal are alternately laminated multiple times, or a platinum group metal layer. Because it has a structure in which alloy layers of elemental metals and alloy layers of platinum group metals and iron group metals are alternately laminated multiple times, a large coercive force is obtained and high-density recording is possible. The present invention has excellent effects such as enabling stable storage.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional structural diagram of the product of the present invention, Figure 2 is a schematic diagram of the sputtering device used to manufacture the product of the present invention, Figure 3 is a graph showing the Kerr hysteresis loop of the product of the present invention, and Figure 4 is a conventional product. 3 is a graph showing the Kerr hysteresis loop of FIG. 1...Substrate 2...Co layer 3...Pt-Pd alloy layer Patent Applicant Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. It is characterized by having a laminated film in which a single layer of a metal of a platinum group element and an alloy layer of a metal of an iron group element and a metal of a platinum group element are alternately laminated multiple times. Magneto-optical recording medium. 2. A light characterized by having a laminated film in which mutual alloy layers of platinum group metals and single metal layers of iron group elements or alloy layers of this and platinum group metals are alternately laminated multiple times. magnetic recording medium.