JPH0447547A - Magneto-optical recording film - Google Patents

Abstract

PURPOSE:To obtain a sufficiently high magneto-optical effect for light of a short wavelength region and to obtain large perpendicular magnetic anisotropy by controlling the boundary energy of the respective layers of alternately laminated multilayered films. CONSTITUTION:Iron family elements 2 and platinum family element layers 3 are alternately laminated on a substrate 1 by using at least one kind of the elements selected from Pt, Pd, Rh, and Au and at least one kind of the elements selected from Fe or Co. Cases contg. N2 in gaseous Ar are ionized and the substrate is irradiated with the ions as a method for treating the layer boundaries to form boundary energy control layers 4 on the respective layer boundaries. The large perpendicular magnetic anisotropy is obtd. in this way and the stability as the perpendicularly magnetized film is assured. Further, the magneto- optical effect is improved and the value thereof is larger as the light of the shorter wavelengths is used. Ultra-high density magneto-optical recording is possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is particularly suitable for increasing recording capacity by using short wavelength light in magneto-optical recording in which recording, reproduction or erasing is performed using laser light. The present invention relates to a magneto-optical recording film.

[Conventional technology]

With the recent development of an advanced information society, the need for high-density, large-capacity file memory is increasing. Optical recording is attracting attention as a memory that can meet this demand, and following read-only types and write-once types that can record only -degrees, a magneto-optical type that can be freely rewritten has recently been commercialized. Currently, this reversible magneto-optical disc is being researched by many institutions with the aim of improving its performance. One of these is to increase the recording density, and the use of short-wavelength light for recording and reproducing is seen as promising and is at the center of research. In this case, Tb-Fe-
In alloy films of rare earth elements such as Co-based elements and iron group elements, the magneto-optic effect obtained decreases as the wavelength of the light used becomes shorter, so that good reproduction may not be possible.

A known example that solved this problem is EP-0304873
can be given.

[Problem to be solved by the invention]

In the above-mentioned conventional techniques, the magneto-optical effect obtained when short wavelength light is used is not necessarily sufficient, and the perpendicular magnetic anisotropy does not necessarily exist stably as a perpendicularly magnetized film. As a result, highly reliable disks may not be obtained, which has been one of the obstacles to practical application.

An object of the present invention is to provide a magneto-optical recording film that can obtain a sufficiently large magneto-optical effect for light in a short wavelength region and has perpendicular magnetic anisotropy large enough to exist stably as a perpendicularly magnetized film. be.

[Means to solve the problem]

In response to the increasing need for high-density, large-capacity file memory due to the recent development of an advanced information society1
One type of memory is optical memory.

In recent years, magneto-optical recording has been put into practical use as rewritable optical recording. Currently, efforts are being made to improve the performance of magneto-optical recording, particularly to increase the density. In this case, in alloy systems of rare earth elements and iron group elements, such as the Tb-Fe-C0 system, which has been widely used, the wavelength of the light used is short (
As the temperature increases, the magneto-optic effect becomes smaller, and stable reproduction output may not be obtained. This point was one of the obstacles to practical application, but this was solved by using a multilayer film in which PT and Co were alternately laminated as a recording film. However, this recording film did not have a sufficiently large perpendicular magnetic anisotropy to exist as a perpendicularly magnetized film, and the magneto-optical effect did not necessarily have a sufficiently large value.

In order to solve this problem, in the present invention, the interfacial energy of each layer in the alternately laminated multilayer film is controlled. By controlling the interfacial energy, it is possible to increase the perpendicular magnetic anisotropy, and as a result of the control, the optical complex refractive index can be distributed in the film thickness direction, and the processed layer obtained as a result of controlling the film thickness and interfacial energy. By controlling the optical properties of the film, it is possible to generate multiple interference in the film. As a result, the magneto-optical effect exhibited by the recording film becomes significantly large.

As a method for controlling the above-mentioned interfacial energy, a method of making oxygen or nitrogen exist as a compound or a solid solution near the interface can be used. Specific methods for this include irradiation with these elements as an ion beam, ion implantation, and atmosphere control during film formation.

Through these methods, by making oxygen and nitrogen exist as a compound or solid solution near the interface of each layer, the interfacial energy increases, and the perpendicular magnetic field anisotropy energy increases due to stress changes, resulting in a stable perpendicularly magnetized film. I can do it. In addition, due to the presence of these elements, this recording film had reduced activity against oxygen and water in the atmosphere, and exhibited high corrosion resistance.

[Effect]

By allowing oxygen or nitrogen to exist as a compound or solid solution near the interface, perpendicular magnetic field anisotropy is induced due to changes in interfacial tension, etc. and changes in interfacial energy, so it can exist stably as a perpendicularly magnetized film. . Furthermore, since the optical complex refractive index differs due to the presence of the interface treatment layer, by causing multiple interference in the recording film,
The magneto-optic effect can be increased. This improves the reliability of the recording film and enables good reproduction.

Hereinafter, the details of the present invention will be explained using examples.

〔Example〕

FIG. 1 is a schematic diagram showing the cross-sectional structure of the magneto-optical recording film produced in this example. The recording film was produced using a two-dimensional simultaneous sputtering method. First, iron group element layers 2 and platinum group element layers 3 were alternately laminated on a substrate 1 . Single targets of pt and Co were used. A to the discharge gas
r (purity 99.999% or more), discharge gas pressure 5
mTorr, input power density is pt is 4, 6 W/
al and G o are 3.2 W/cd. Then, as a layer interface treatment method, Ar gas containing 0.5 von% N2 is ionized and irradiated onto the substrate so as not to interfere with the sputtered particles of PT and Co, thereby forming an interfacial energy control layer 4 at each layer interface. Formed. The thickness of each PT layer is 12 people.

The Co layer had 4 layers, and the total film thickness was 150 layers.

Regarding the magneto-optical recording film produced in this way, Kerr (K)
err) effect was measured.

FIG. 2 shows the Kerr hysteresis loop of the recording film obtained. First, the hysteresis of the film produced by controlling the interfacial energy has good squareness, as shown by the solid line in the figure, and the Kerr rotation angle θ is ~0.80°.
Met. This is a hysteresis loop measured using light with a wavelength of λ=400 nm. On the other hand, N
2. The dotted line in FIG. 2 shows the hysteresis loop of a recording film produced without ion beam irradiation. Due to its shape, the perpendicular magnetic anisotropy is small, and the Kerr rotation angle = θ is also 0.
, 52°, and both the magnetic and magneto-optical properties were inferior to those of the film produced according to the present invention.

In the embodiments of the present invention, the increased Kerr rotation angle is not due to increased perpendicular magnetic anisotropy, but is due to multiple interference effects. Furthermore, the coercive force of the magneto-optical film produced using the present invention is 6 KOe, whereas that of the film produced without controlling the interfacial energy is 1.2 KOe.
KOe was significantly smaller.

Next, FIG. 3 shows the wavelength dependence of the Kerr rotation angle of the recording film produced using the present invention. From this figure, λ=9
From 00 to 700 nm, θ is almost constant at ~0.60@, but when it becomes shorter than 700 nm, K suddenly decreases.
The err rotation angle increases to 0.8 at λ” 400 nm
It became 0'.

Next, a disk was manufactured using this recording film.

The structure was made by forming silicon nitride to a thickness of 500 mm on a glass or plastic disk substrate with uneven guide grooves, and then forming the recording film shown above.5.25
An inch-sized disk was produced. Radius of this disk: r = 30 m position, recording frequency: 20 MHz, laser power near, 5 m W, pulse width: 50 ns
It was recorded at. When the recorded magnetic domain of this recorded disk was observed using a polarizing microscope, it was found that the recorded magnetic domain was 0.3 μm long and 0.3 μm long.
It was confirmed that a minute magnetic domain with a width of 5 μm was formed.

When the information recorded on this disc was reproduced at 1.5 mW power, the carrier-to-noise ratio (C/N ratio) was 52 dB.
Met. When the track pitch was further reduced and pit-edge recording was performed, the recording capacity was several times greater than that of the current magneto-optical disk of the same size. Similar effects were obtained with this recording film using a magnetic field modulation recording method.

This effect may be obtained by using Pd, Rh, or Au in addition to pt. Furthermore, these alloys may also be used. Furthermore, C
Similar effects can be obtained by using Fe in place of o. Also,
By adding impurity elements such as Nb, Cr, Ti, Ta, etc., it is possible to improve corrosion resistance and control magnetic properties such as the Curie temperature. Furthermore, although nitrogen is used in this embodiment to control the interfacial energy, the same effect can be obtained by using oxygen in addition to this.

When the recording film of the present invention or a disk using this recording film was left at 80° C. and 95% RH (relative humidity) for 1000 hours or more, there was no change in magnetic properties or error rate. By allowing nitrogen or oxygen to exist near the interface in this way, the interfacial energy could be controlled, which was also effective in improving reliability.

〔Effect of the invention〕

According to the present invention, since a large perpendicular magnetic anisotropy can be obtained, stability as a perpendicularly magnetized film can be ensured, and the coercive force is also 3 KOe or more, so recorded data can be stably retained. Furthermore, the magneto-optic effect could be increased, and its value became larger as light with a shorter wavelength was used. This made it possible to obtain ultrahigh-density magneto-optical recording. Furthermore, the presence of the interfacial energy control layer suppresses the diffusion of oxygen into the layer, thereby improving the corrosion resistance of the film and simplifying the disk structure, which is also effective in reducing the cost of the disk.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a magneto-optical recording film according to an embodiment of the present invention, and FIG.
The figure shows the Kerr hysteresis loop of the magneto-optical recording film of the example of the present invention, and FIG. 3 is a characteristic diagram showing the wavelength dependence of the Kerr rotation angle of the magneto-optical recording film of the example of the invention. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Iron group element layer, 3...Platinum group optical layer, 4--Substrate Z--removal 3--Monochontal metal group lA 4-11 interface corrosion 4 Le t"-s Kuda 7 pieces 16 straw wards Youzuke/7'J skin length, ゛enter (nm)

Claims (1)

[Claims] 1. Pt, Pd, and R as materials for magneto-optical recording that records, reproduces, or erases information using laser light and a magnetic field.
h, at least one element selected from Au and F
1. A magneto-optical recording film characterized in that the interfacial energy of each layer is controlled in a multilayer film in which at least one element selected from e or Co is laminated alternately. 2. A magneto-optical recording film characterized in that, as a method for controlling interfacial energy at layer interfaces according to claim 1, oxygen or nitrogen is present as a compound or solid solution near each layer interface. 3. To make oxygen or nitrogen exist near the interface of each layer as described in claims 1 and 2, convert it into a compound or solid solution by using an ion beam, ion implantation method, or atmosphere control during film formation. A magneto-optical recording film characterized in that interfacial energy is controlled by. 4. By controlling the interfacial energy of each layer as described in Claims 1 and 2, the optical constants are controlled. More preferably, by controlling the optical complex refractive index, multiple interference of light is caused in the magneto-optical recording film. A magneto-optical recording film characterized by: