Kokusai Denshin Denwa Kabushiki Kaisha

Kokusai Denshin Denwa Co., Ltd.

Nobutake Imamura

Shinsuke Tanaka

Chuichi Ota

Yoshinori Mimura

Toshihiko Kobayashi

Fujio Tanaka

Yasuyuki Nagao

A magneto-optical recording medium, which comprises a thin film constituted of an amorphous alloy (R.sub.x TM.sub.1-x).sub.1-y A.sub.y (where the element material R is at least one rare earth element, the element material TM at least one 3d transition metal and the element material A at least one semi-metal-semiconductor element) and having an easy axis of magnetization in a direction perpendicular to the film surface, the atomic ratio being 0.15.ltoreq.xx.ltoreq.0.35 and 0.00&lt;y.ltoreq.0.20.

Magneto-optical recording medium

A magneto-optical recording medium is disclosed in which a magnetic thin film recording layer is formed by a magnetic material having a Curie temperature or magnetic compensation temperature as low as 50.degree. to 250.degree. C. and a coercive force as large as 1 KOe or more and having an easy axis of magnetization perpendicularly to the film surface. A substantially transparent magnetic material film layer of ferrite, garnet or the like is disposed adjacent the recording film layer, large in the Faraday rotation angle and having an easy axis of magnetization perpendicularly to the film surface. A transparent substrate is disposed on the side of incidence of light. The substantially transparent magnetic material layer of the ferrite, garnet or the like may increase the magneto-optical rotation angle in the magnetic thin film recording layer, or may increase the magneto-optical rotation angle by the Faraday effect. The thickness of the substantially transparent magnetic material layer is selected in such a region where the figure of merit .sqroot.R.multidot..theta..sub.k expressed by its reflectivity R and the magneto-optical rotation angle .theta..sub.k is maximum.

A magneto-optical recording medium, in which a transparent synthetic resin substance, a light transparent thin film of a simple substance of metal or a metal compound, a dielectric layer, a recording medium layer formed of an amorphous alloy having an easy axis of magnetization in a direction perpendicular to the layer surface and thick enough to reflect light, and a protective film are provided in this order from the light incidence side. The dielectric layer may be provided with an auxiliary recording medium layer formed of the amorphous alloy having an easy axis of magnetization in the direction perpendicular to the layer surface and thin enough to permit the passage therethrough of light.

A magneto-optical recording medium comprising: a recording layer of a magnetic thin film low in the Curie temperature or magnetic compensation temperature and high in coersive force and having an easy axis of magnetization in a direction perpendicular to the film surface; a reproducing layer disposed adjacent the recording layer and large in the magnetic Kerr rotation angle and having an easy axis of magnetization in a direction perpendicular to the film surface; and a transparent substrate disposed on the side of incidence of light. In accordance with the present invention, a reflecting metal layer is provided for reflecting light having entered from the side of the transparent substrate and passed through the recording layer and the reproducing layer. A dielectric layer may be further disposed at least on one side of the transparent substrate or the reflecting metal layer with respect to the recording layer and the reproducing layer. The order of the recording layer and the reproducing layer may be replaced by each other.

Amorphous thin film with easy magnetization axis perpendicular to film surface for magneto-optical recording with low recording power and high S/N in reading signal is set forth. The medium is an alloy of heavy rare earth element and iron with substitution of some heavy rare earth elements by light rare earth element, and the preferable chemical formula of the thin film is (R.sub.z A.sub.1-z).sub.x Fe.sub.1-x, or [(R.sub.z A.sub.1-z).sub.y B.sub.1-y ].sub.x Fe.sub.1-x where R is a light rare earth element, A and B are heavy rare earth elements, and the atom ratios satisfy 0.15.ltoreq.x.ltoreq.0.35, 0.00&lt;y&lt;1.00, 0.00&lt;z&lt;1.00. Recording is effected by using Curie point, or magnetic compensation temperature, and reading of information is effected by using the Kerr effect.

A magneto-optical recording medium having an easy axis of magnetization in a direction perpendicular to the film surface, characterized in that a readout medium layer, a reflection layer and a recording medium layer are sequentially disposed in a direction of the incidence of a reading-out light, thereby to increase a reproduced output.

A magneto-optical recording and reproducing apparatus for recording information on a recording medium made of a magneto-optical recording material. The apparatus is provided with at least two lasers for carrying out simultaneously a combination of two functions of the apparatus such as recording-reproducing or reproducing-erasing or erasing-recording functions. The recording and erasing is effected optically by independent light beams. Provision is made for recording and erasing the information by light beam and by use of an application of magnetic fields of different coercive values. The lasers are modulated or not independently and an optical system is provided through which the write-in and readout takes place and focusing is in response to the reflected light from the record on the recording medium.

Magneto-optical recording and reproducing system

A multi-layer magneto-optical recording medium is constructed by placing a transparent protective film upon a magneto-optical recording medium wherein the easy axis of magnetization is provided perpendicular to the film surface so as to make the direction of magnetization perpendicular thereto to take a binary code depending on whether the vertical direction thereof is upward or downward, and further by placing a metal film, of which melting point is lower than either said magneto-optical recording medium and said transparent protective film, upon said transparent protective film. The metal film is evaporated by a laser beam irradiated thereon in a manner to leave a portion thereof not evaporated to become a tracking guide, whereby reproducing a magneto-optical record free of disturbance on linear polarization. The metal film can be perforated to form pits by irradiation of a laser beam. Presence or absence of such pits can be used for storing data and, therefore, is applicable for a read-only memory of optical method or an optical video disc.

Multi-layer magneto-optical recording medium

Disclosed is a magneto-optic recording medium to which magnetic Kerr effect is applied and characterized by the tracking guide on an even surface free from disorder of linear polarization. Since the tracking guide may be any type if it has a different reflection characteristic from that of the memory area viewing from magneto-optic standpoint, the tracking guide can be produced by a thermal treatment for changing the magnetic property of a part of a thin film with its magnetization easy axis in the direction perpendicular to the film surface. As no difference exists between the memory area and the guide area other than their magnetic properties, they are on the same plane and have no unevenness between their surfaces. Where, the guide area is assumed to have such magnetic property as the magnetization easy axis is parallel to the film surface, or it is perpendicular to the film surface but has no rectangular hysterisis. Such change of magnetic property can be obtained easily by an irradiation of laser beam to an amorphous alloy thin film with perpendicular magnetization easy axis.

Magneto-optic recording medium

A magnetic transfer record film employed for magneto-optically reading magnetic record patterns. The magnetic transfer record film is formed, as the principal component, of an alloy of a heavy rare earth metal and a transition metal and has an easy axis of magnetization in a direction perpendicular to the film surface and further has an alloy composition included in a range of .+-.10% at the periphery of a center alloy composition where the saturation magnetic moment becomes minimum with respect to a change of the composition within a temperature range used. The magnetic transfer record film is deposited on a transparent substrate and positioned closely to a magnetic record medium on which a magnetic record pattern to be observed is stored, so that the magnetic record pattern is transferred to the magnetic transfer record film. An optical system is provided to magneto-optically read out the transferred magnetic record pattern from the magnetic transfer record film.

Magnetic transfer record film and apparatus for magneto-optically

A magnetic head for reading out the state of magnetization recorded on a magnetic recording medium, in which the magnetic head comprises a substrate of insulating material, an amorphous magnetic thin film, a pair of current terminals, and a pair of voltage terminals. The amorphous magnetic thin film is deposited on the substrate so as to have a width smaller than respective unit areas of magnetic records on a magnetic recording medium to be separately read out therefrom and to have an easy axis of magnetization in a direction perpendicular to the film surface. The current terminals are formed on the substrate for flowing a current in the amorphous magnetic thin film in the lengthwise direction thereof. The voltage terminals are formed on the substrate for deriving from the amorphous magnetic thin film a voltage induced in the transverse direction thereof.

Thin film magnetic head

A magneto-optical memory medium having an easy axis of magnetization perpendicular to the medium surface. The memory medium is formed by an amorphous Dy-Fe system alloy film containing 18 to 28 atom % Dy.

Magneto-optical memory medium

A magnetic transfer record film employed for magneto-optically reading magnetic record patterns. The magnetic transfer record film is formed, as the principal component, of an alloy of a heavy rare earth metal and a transition metal and has an easy axis of magnetization in a direction perpendicular to the film surface and further has an alloy composition included in a range of .+-. 10% at the periphery of a center alloy composition where the saturation magnetic moment becomes minimum with respect to a change of the composition within a temperature range used. The magnetic transfer record film is deposited on a transparent substrate and positioned closely to a magnetic record medium on which a magnetic record pattern to be observed is stored, so that the magnetic record pattern is transferred to the magnetic transfer record film. An optical system is provided to magneto-optically read out the transferred magnetic record pattern from the magnetic transfer record film.

Growing community of inventors

Tokyo, Japan

Nobutake Imamura