JPS60101743A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a photomagnetic recording medium having both improved Kerr rotating angle and S/N ratio by forming a thin 4-components amorphous alloy of Gd-Tb-Sm-Fe having the axis of easy magnetization in the direction perpendicular to the film plane on a base plate. CONSTITUTION:Respective components are sputtered onto a base plate 4 through circular through-holes 6, 6 provided to a disc-shaped shielding plate 5 from the 1st target 2 consisting of, for example, Gd, Tb and Fe and the 2nd target 2 consisting of Sm by using a magnetron sputtering device to form a thin quaternary amorphous alloy film of Gd-Tb-Sm-Fe contg. 10-40atom% rare earth metal including Gd, Tb and Sm and contg. Sm in the rare earth metal at <=65atom% and not zero on the surface of a base 5, thereby forming the photomagnetic recording medium having the axis of easy magnetization in the direction perpendicular to the surface of the base. The Kerr rotating angle is thus increased and S/N is improved and the above-mentioned medium is produced with good productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording medium made of an a(+d-Tt)-Sm-Fe47e amorphous alloy.

In recent years, in order to record large amounts of information at high density, magneto-optical recording has been researched and developed, in which bits are written by projecting a laser beam to locally heat the recording medium and read out using the magneto-optic effect. . Rare earths are used in the recording medium.
There is an amorphous film made of a transition metal, which is attracting a lot of attention because it is suitable for mass production and has advantages such as low readout noise.

As a prior art of such an amorphous film, Japanese Patent Application Laid-Open No. 126-1983
No. 907 I-G'i-Tb-Fe E7G thread alloy thin film has been proposed, which takes advantage of the characteristics of both Tb-Fe, which has excellent recording characteristics, and GdFe, which has a large Kerr rotation angle in reproduction characteristics. In practical terms, a satisfactory Kerr rotation angle has not yet been obtained, and there is an even greater desire to improve its characteristics.

Therefore, in view of the above circumstances, the inventors of the present invention, as a result of diligent research, found that G6-- which has one cucumber point around 160 degrees Celsius.
It has been found that the Kerr rotation angle can be improved by adding Sm to the Tb-Fe ternary alloy thin film.

The present invention was completed based on the above findings, and is based on the GCI
It is possible to provide a magneto-optical recording medium based on a -Tb-Fe ternary alloy thin film that further improves the Kerr rotation angle, improves the S/N ratio, and has improved reproduction characteristics. .

The gist of the present invention is to provide a magneto-optical recording medium comprising a 0α-Tb-Sm-Fe quaternary amorphous alloy thin film having an axis of easy magnetization in a direction perpendicular to the film surface. .

The present invention will be explained in detail below.

According to the present invention, an Od-Tb-Sm-Fe quaternary amorphous alloy thin film (hereinafter abbreviated as Qd-Tb-Sm-re alloy thin film) having an axis of easy magnetization in a direction perpendicular to the mirror surface is formed on a substrate. By setting various conditions using the magneto-optical recording medium I which will be described later, an excellent Kerr rotation angle can be achieved.
A magneto-optical recording medium is obtained. Kayo fz Gi −
Take Th-3m -F'e alloy alloy I, Ga-Tb
and rare earth metals containing Sm are lθ~40 atomic
%, and if it deviates from this range, the formation of an amorphous perpendicularly magnetized film will become a problem, the Kerr rotation angle will become small, and the squareness ratio and coercive force will also deteriorate. It is preferable to set the glue in the range of 15 to ao atomic%.

Furthermore, according to the present invention, in addition to setting the range of rare earth elements as described above, Sm in this rare earth element is set to 65
It is important that the content be less than 65 atomic% (not including 0); if it exceeds 65 atomic%, not only will the Kerr rotation angle not be improved, but the squareness ratio and holding force will also deteriorate. Among the elements, Sm is 5 to 25
It is preferable to contain it in a range of atomic%.

Next, a method for manufacturing the above-mentioned magneto-optical recording medium of the present invention will be explained with reference to the drawings.

The figure shows a magnetron sputtering apparatus for producing an A-Tb-Sm-Fe alloy thin film;
Inside the vacuum chamber (1), a first target (31) consisting of Gd, Tb, and Fe and a second target (31) having a length of <21.8 m is provided.
A disk-shaped substrate (41) on which a -Fe alloy thin film is formed, and a rotatable disk-shaped shielding plate (5) are arranged.

The shielding plate (5) I is the 1st and 2nd target (2113
A pair of circular through holes (6) are formed right above each of the targets 1 and 2 during film formation.
Various metals scattered from the YT communication hole 6) pass through the YT communication hole 6) and are deposited on the rotating substrate f'1l-1. 1.2 Kuugetsu l-(21
) is coated on top to prevent vapor deposition.

A high frequency V1 working pressure is applied between the first target (2) and the substrate (4), and between the second target (3) and the plate (4) from the high frequency power supply (7) (8), respectively. At the same time, a 1r [current power source (
9) is attached.

This ffl, 2 targets T21 (3+ lower side is based on 1 planar magnetron type cathode, permanent magnet made of alnico, fugulite, samarium cobalt (
101 fl l is attached to f (ii), thereby increasing the ionization efficiency of discharge gas molecules by utilizing the Penning discharge phenomenon in which the electric field and magnetic field are orthogonal, and high-speed film formation suitable for mass production becomes nf capability.

The first target (2) composed of CM, Tb, and Sm used in the present invention is, for example, made of a circular plate made of Fe in the shape of a rectangular G (11[chip] and an appropriate number of T'b chips). It is constructed by placing a G1 chip and a Fe% chip on a TI) disc, or a Tb chip and an Fe chip on a Gd disc. In addition, the shape of the chip may be changed to any shape such as a fan shape instead of a square shape.
The same effect can be achieved by using a disc made of an h-Sm alloy.

Next, the operation of the above magnetron sputtering apparatus will be explained. First, the vacuum chamber (1) is approximately I x 10 Torr.
After being evacuated to below r, high-purity Ar is placed inside.
gas and/or N9 gas, or a mixture of N2 gas and N2 gas to control the magnitude of perpendicular magnetic anisotropy energy as necessary (hereinafter, these introduced gases are abbreviated as atmospheric gas), vacuum chamber (1) The interior is maintained at a predetermined gas pressure. Subsequently, the shield plate (5) is rotated about 90 degrees, and the first and second targets (21+31) are press-sputtered with the substrate (4) shielded, thereby etching the oxide layer on the surface of each glue target.

After that, insert the pair of through holes (6) into the shield plate (5) so that they are directly above the 1.2nd target (f2) +31.
) to rotate and place. Next, a predetermined substrate rotation speed and high frequency power are set to obtain an appropriate film formation rate, and simultaneous discharge is performed on the 1st and 2nd targets (21+3 targets) for a predetermined time. As a result, the atmospheric gas becomes plasma, The positive ions hit the 1.2 targets +21 +31, and various target materials released are deposited on the substrate (4).

In the present invention 1, in order to obtain a suitable magneto-optical recording medium having a large Kerr rotation angle, high retention, and excellent squareness ratio, it is necessary to apply a positive or negative polarity to the substrate (4). It is better to apply a bias voltage of 3 and set the atmospheric gas pressure within a predetermined range; if the atmospheric gas pressure is less than 1 x 10 Torr, a stable discharge state cannot be obtained and film formation may be difficult. , 50 x 1O
When the temperature exceeds −8 Torr, the magnetic thin film contains argon (Ar), nitrogen (N+), and oxygen (0
) increases and the film properties deteriorate, making it difficult to obtain a large Kerr rotation angle and a large coercive force.
oe 50X 10 TOrr, preferably 3X1
It is set in the range of 0 to 20 x 10 categories.

The deposition rate of the Gd-Tb-Sm-Co alloy thin film depends on the rotational speed of the substrate (4), but in the present invention, the rotational speed of the substrate is set as a basis. In addition, 0.1A
If it is less than 30 A/rotation, it becomes difficult to form a perpendicularly magnetized film because impurities are easily introduced, and even if it exceeds 30 A/revolution, it becomes difficult to form a perpendicularly magnetized film.

The temperature of the substrate (4) during film formation is set to 200° C. or lower. When the temperature exceeds 200° C., relaxation of the amorphous structure is observed, making it difficult to produce a film with a large coercive force.

Also, during film formation, the first target (2) and the substrate (4)
A high frequency power of 100 W to 5 kW is applied for one moment, and high frequency power of an appropriate magnitude is also applied so that a predetermined amount of Sm is contained between the second target (3) and the substrate (4). be done.

After pressing and sputtering the composite target, applying a bias voltage and setting the atmospheric gas pressure, substrate temperature, high frequency power, etc. within predetermined ranges, the unique amorphous morphology of the substrate can be formed. 06-
Since the aa-Tb-Sm-Fe alloy thin film produced under these conditions has a large Kerr rotation angle, a magneto-optical recording medium with excellent reproduction characteristics can be provided.

Next, examples of the present invention will be described.

〔Example〕

A magnetron sputtering device (not shown in the above figure) is used, and the first target (2) is the upper part of the ocular disc.
Gd 1Jt9 square chip° and Tb [square chip is MIF? The second target (3) is anq+! ! A disk was used.

The gas pressure in the vacuum i v'+ ft+ is Ar gas pressure 7
It was set to 1O-3TOrr, and after press sputtering, the board +
41. While rotating at 50 rpm and applying a bias voltage to the claw plate (4), an effective high frequency power of 400 W is applied to the first target (2), which is applied to the second target (3). By increasing the effective high-frequency power from zero, Gd-Tb-Sm-Fe alloy thin films with increasing Sm content were formed on the substrate (4) as shown in Table 1. When the Gd-Tb-Sm-Fe alloy thin film obtained in this example was measured using X-ray diffraction and a torque meter, it was confirmed that the film was amorphous and perpendicularly magnetized, respectively.

According to the Gd-Tb-Sm-Fe alloy thin film obtained in this way, the composition ratio of G(1, Tb, and Fe can be determined by not using Sm as the second target (3), so that ICP emission spectroscopy is possible. According to, which kama-T
b -Sm-Fe alloy thin film (Gdbo T'bbo
)! ! 6Fe7+, and based on this composition, the Kerr rotation angle of the Gd-T'b-Sm-Fe alloy thin film was measured using a Kerr rotation angle measurement device manufactured by JASCO Corporation. This is the result.

In addition, in Table 1.

The Sm content in the word-Tb-Sm-Fe alloy thin film is
If this is X, Smx ((Gd+)o Tbb
o)26Fe741Too-X.

In Table 1, sample number l is outside the scope of the present invention.
)-Fe alloys, and it can be seen that the Kerr rotation angles are even larger for samples Nos. 2 to 6 of the present invention compared to this Kerr rotation angle.

As is clear from the above embodiments, according to the two embodiments of the magneto-optical recording device of the present invention, Kerr rotation is achieved by adding a predetermined amount of Snl to a Gd-Tb-Fe ternary amorphous alloy thin film. It is possible to provide a magneto-optical recording medium with a larger angle, a further improved S/R ratio, and excellent reproduction characteristics.

Furthermore, as the Kerr rotation angle increases, the Curie point tends to rise, but since the magneto-optical recording medium of the present invention uses a -Tb-Fe alloy with a relatively low Curie point, the Curie point tends to increase. Even if the Curie point increases as the rotation angle increases, if a semiconductor laser is used as the light projection source, the Curie point can be controlled within a range that does not cause any practical problems. As a result, there is no need to use a multi-layered recording medium due to the increase in Curie point, and the magneto-optical recording medium of the present invention can be used for recording and reproduction with a single-layered structure, and the manufacturing process can be improved. Simplification is possible.

[Brief explanation of the drawing]

The figure is a schematic diagram of a magnetron sputtering apparatus for producing magneto-optical recording media. (2)...First target, (31-...Second target, ;4)...Substrate, (71, +81-...High frequency power supply, 19)-...DC power supply Patent applicant Kyocera Co., Ltd. Procedural Amendment (Voluntary) December 1981 70 1. Indication of the case 1981 P.C.I.P. 207cI159
No. 2, Title of the invention Magneto-optical recording medium 5, Subject of amendment Application 1 and specification 6.7 + Ii Correct content As attached, typed application and specification

Claims (1)

[Scope of Claims] (1) A magneto-optical recording medium comprising a Gd-Tb-Sm-Fe quaternary amorphous alloy thin film having an axis of easy magnetization in a direction perpendicular to III''! (21nil (jd -Tl) -Sm -Fe quaternary thread amorphous alloy thin film is (kl, , 'J, 'b and S
2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium contains 10 to 40 atomic% of a rare earth metal containing C. (3) Among the rare earth metals, Sm is 65 atomic
% or less (not including 0) of the magneto-optical recording medium according to claim 2.