Chemistry: electrical and wave energy – Processes and products – Vacuum arc discharge coating
Patent
1985-09-17
1986-08-26
Demers, Arthur P.
Chemistry: electrical and wave energy
Processes and products
Vacuum arc discharge coating
204192R, C23C 1500
Patent
active
046081429
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of manufacturing a magneto-optic recording film wherein a Bi-substituted rare-earth iron garnet film with an easy axis of magnetization normal to the film plane is formed on a substrate (hereafter, the vertically magnetized film denotes the film with an easy axis of magnetization normal to the film plane).
BACKGROUND ART
Iron garnet R.sub.3-x Bi.sub.x (Fe, M).sub.5 O.sub.12 obtained by substituting Bi for R in a rare-earth iron garnet R.sub.3 (Fe, M).sub.5 O.sub.12 is recently receiving much attention as a magneto-optic recording material. Note that in the above formulae, R is a rare-earth element, and M is an atom having a valence of 3 or a group of atoms having a valence equivalent to a valence of 3 such as Al.sup.3+, Ga.sup.3+, Sc.sup.3+, Tl.sup.3+, (Co.sup.2+ +Ti.sup.4+) or the like. In the Bi-substituted rare-earth iron garnet, since some Rs are substituted with Bi, the Faraday rotation angle .theta..sub.F can be increased without much increasing the absorption coefficient .alpha. and, therefore, this material is generally an excellent magneto-optic recording material.
In order to improve performance of a magneto-optic material of the Bi-substituted rare-earth iron garnet having such a property, the Bi substitution amount x must be increased, which results in the increase of the Faraday rotation angle .theta..sub.F. Conventionally, in a sintered ceramics of a rare-earth iron garnet, the Bi solid solution limit is known to be 50% of the dodecahedral site of the crystal structure. So monocrystalline films having a large Bi substitution amount x have been studied intensively.
A highly Bi-substituted rare-earth iron garnet thin film as described above is normally manufactured by the liquid phase epitaxy (LPE) method as described, e.g., in J.J. A. P., 19, 2105 (1980). However, a magnetic thin film manufactured by the liquid phase epitaxy method, wherein the film composition is Bi.sub.0.6 Sm.sub.1.2 Er.sub.1.2 Ga.sub.1.0 Fe.sub.4.0 O.sub.12 has a small Faraday rotation angle .theta..sub.F of about 2.4 degree/.mu.m at a light wavelength .lambda.=500 nm at which the Faraday rotation angle is expected to be maximum value. Such a small Faraday rotation angle is impractical.
Further, in LPE method, a Bi-substituted rare-earth iron garnet film must be formed on a single crystal substrate such as gadolinium gallium garnet Gd.sub.3 Ga.sub.5 O.sub.12 (to be referred to as a GGG substrate hereafter) which is high is cost. However, a method capable of forming a highly Bi-substituted rare-earth iron garnet thin film on an amorphous substrate such as a glass substrate which has a high productivity has been desired. Although various studies have been made to provide such a method, a Bi-substituted rare-earth iron garnet thin film formed on an amorphous substrate obtained so far has been a polycrystalline film having a magnetization parallel to the film plane. A vertically magnetized film desired as a magneto-optic recording material has not yet been obtained.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a method of manufacturing a magneto-optic recording film which is free from the above-mentioned drawbacks of the conventional methods.
In the conventional LPE method, a thin film must be grown at a high temperature of about 800.degree. C. However, since the vapor pressure of Bi is extremely high, i.e., about 1 Torr, Bi is selectively vaporized from the melt during thin film formation by the LPE method. In view of this problem, the present invention is based on the concept that the LPE method is not suitable for forming a thin film of a Bi-substituted rare-earth iron garnet containing a high concentration of Bi. According to the estimation made by the present inventors, the Bi substitution amount x in a monocrystalline thin film which has been formed so far by conventional LPE methods using a GGG substrate is at best about 20% of the dodecahedral site of the rare-earth iron garnet.
In a method of manufacturing a magneto-optic recor
REFERENCES:
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patent: 4414087 (1983-11-01), Meckel
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Abe Masanori
Gomi Manabu
Demers Arthur P.
Nippon Sheet Glass Co. Ltd.
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