Ricoh Company, Ltd.

Mitsubishi Chemical Industries Limited

Noda Institute for Scientific Research

Hajime Machida

Yasuo Sawada

Yukio Imada

Masayuki Kinoshita

Katsuhiko Takahashi

Daikichiro Nishikawa

Michitaro Nagasawa

Takashi Yano

Hiroshi Kobayashi

Hitoshi Nakamura

Motoharu Tanaka

Atsuyuki Watada

Fumiya Omi

Uee Myong Hwang

A method of magneto-optical recording and overwriting information onto a double-layer magneto-optical recording medium which has laminated first and second magnetic layers having different coercive forces at a lower operation temperature and a higher operation temperature of which one is a recording operation temperature and the other is an erasing operation temperature, without using an initializing external magnetic field. The method includes the steps of recording by applying a laser beam to an area of the recording medium at a power level corresponding to one of these operating temperatures and erasing by applying a laser beam to an area of the recording medium at a different power level corresponding to the other of the operating temperatures, while applying a bias magnetic field to the magneto-optical recording medium with the same magnetization direction during both recording and erasing, the intensity of the bias magnetic field being greater than the coercive forces of the first and second magnetic layers at the lower operation temperature.

Double-layer magneto-optical recording method without using an initial

Method of magneto-optical recording and overwriting

A magneto-optical recording medium is disclosed, which comprises a substrate, and a magnetic layer supported on the substrate, the magnetic layer comprising (1) a first magnetic layer comprising a magnetic oxide with perpendicular magnetic characteristics, having a saturation magnetization Ms of 100 Gauss or less and a coercive force Hc.sub.1 of 1 KOe or less, and (2) a second magnetic layer comprising a magnetic oxide having a thermal conductivity.times.of less than 0.3 cal/cm.sec..degree.C. and a light absorption coefficient .alpha. of 5.times.10.sup.3 cm.sup.-1 or more. This magneto-optical recording medium may further comprises an auxiliary production layer comprising a magnetic material, which is overlaid adjacent to the first magnetic layer.

Magneto-optical recording medium

A magneto-optical recording medium is disclosed, which comprises a transparent substrate, a magnetic oxide layer formed on the substrate, and band-shaped reflection layers formed on the magnetic oxide layer.

A hexagonal ferrite element comprising a hexagonal ferrite film layer and a substrate for supporting the ferrite layer is prepared by applying on the substrate a metal-ion solution comprising an iron (II) ion and at least one ion selected from the group consisting of Ba.sup.2+, Sr.sup.2+, Pb.sup.2+, La.sup.3+ and Ca.sup.2+, with the pH of the solution set at 7 or more, thereby oxidizing the iron (II) ion contained in the metal-ion solution to iron (III) ion. For controlling the magneto-optical characteristics of the produced hexagonal ferrite film, other ions such as Co.sup.2+, Co.sup.3+, Al.sup.3+, In.sup.3+ and Ti.sup.4+ may be added to the above metal ion solution, thereby replacing part of iron atoms contained in the ferrite film by such atoms added in the form of ion. Further, for a more controlled and efficient production of the ferrite film, an oxidizing liquid for oxidizing the iron ion, Fe.sup.2+, contained in the metal-ion solution, to Fe.sup.3+ can be used by supplying the oxidizing liquid to the substrate concurrently with or after the application of the metal ion solution.

Method of preparing hexagonal ferrite element

A magneto optical recording medium comprising laminating a reflective layer, a dielectric undercoat layer and a hexagonal magnetoplumbite-type metal oxide magnetic layer on a substrate in order, characterized by that said magnetic layer is made an excellently C axis - orientated perpendicular magnetic film by putting the crystal misfit between said reflective layer and said dielectric undercoat layer formed thereon within .+-.30% and the crystal misfit between said dielectric undercoat layer and said hexagonal magnetoplumbite -type metal oxide magnetic layer formed thereon within .+-.30%, and thus various characteristics are widely improved.

Magneto optical recording medium

A method and apparatus for recording information on a magnetic recording medium with high density is provided. A heat spot of predetermined area is applied to the recording medium to raise the local temperature of the recording medium where the heat spot is applied above the Curie point of the recording medium. The heat spot is moved along the recording medium and a magnetic field is applied when a part of the recording medium heated by the heat spot is in the neighborhood of the Curie point in its cooling process, thereby recording information on the recording medium. In accordance with the present invention, an element or bit of information to be recorded on the recording medium is formed by a portion of the heat spot; thus, it relaxes recording conditions and allows to increase recording density.

Thermomagnetic recording

The improvement in a process for the production of 17-hydroxyandrosta-1,4-dien-3-one and androsta-1,4-diene-3,17-dione by the microbiological oxidation of a sterol, its 4-en-3-one derivative or its 1,4-dien-3-one derivative, which comprises adding to the culture medium at least one glyceride-containing substance selected from the group consisting of glycerides, fats, oil seeds and oil fruits in an amount sufficient that the culture medium contains at least 0.3 percent by weight of glycerides.

Growing community of inventors

Tokyo, Japan

Hajime Machida