Abstract: A magnetic thin film memory wherein the memory is composed of magnetic thin films with a layer of a higher coercive force and a layer of a lower coercive force via a nonmagnetic layer laminated repetitively, or magnetic thin films having the easy magnetization axis which lies between the perpendicular and the horizontal directions of the magnetic thin film, and information is recorded on the layer of a lower coercive force, or information is recorded by changing the direction of the magnetization by means of a magnetic field applied by two recording lines which cross the magnetic thin film, thereby to obtain a sufficient amplitude of reproduction signal even when the size of the memory is reduced.

Abstract: An information storage system for recording and reproducing information by use of irradiating light on a medium capable of overwriting information is provided. The information storage system is capable of recording information even if the light intensity is varied so as to enhance reliability. The intensity of the light at the time of overwriting is modulated, the more intense light intensity being P.sub.H and the less intense light intensity being P.sub.L. The system includes a mechanism to keep relationship of P.sub.H +.alpha.P.sub.L equal to a constant (.alpha. being a constant depending on the recording conditions). The laser drive circuit is so adjusted that P.sub.H and P.sub.L always provide an optimal condition even if P.sub.H and/or P.sub.L vary. Thus recording can always be performed under optimal conditions to enhance the reliability of the information storage system to expand the power margin of a recording medium and to increase the percentage yield of information medium.

Abstract: A megneto-optic recording medium which is comprised of a first, a second, a third and a fourth magnetic layers coupled each other between the adjacent layers by an exchange force, wherein said first through fourth magnetic layers satisfy T.sub.c1 <T.sub.c2, T.sub.c3 <T.sub.c2, T.sub.c1 <T.sub.c4 and T.sub.c3 <T.sub.

Abstract: This invention relates to a multi-layer magneto-optic recording medium having an information recording layer and an initializing layer that can be overwritten by light modulation, and in which adjacent layers, including auxiliary layers provided for more efficient transfer from the initializing layer to the recording layer, are coupled by an exchange force. This structure enables high-density, high-speed recording of audio information, visual information, and computer data.

Abstract: In a magneto-optical recording system for recording information with bits having upward magnetization and having downward magnetization on a recording layer of a magneto-optical recording medium, having four magnetic layers exchange-coupled with each other. A laser beam directed onto the medium is modulated to heat the magneto-optical recording medium to two values, for "High" writing and for "Low" writing. During "High" writing, the first to third layers lose magnetization because their Curie temperatures are exceeded, and the direction of the magnetization of the first layer, which is the recording layer is determined mainly by the magnetostatic coupling from the the fourth layer. During "Low" writing, the first and the third layers lose their magnetization as their Curie temperatures are exceeded, and the direction of the magnetization of the first layer is determined by the exchange coupling from the second layer, which in turn is dependent on the exchange coupling from the fourth layer.

Abstract: This invention relates to a magnetooptical recording medium that is capable of direct overwriting by light intensity modulation without using a separate source for generating an external magnetic field and that has four magnetic layers superposed on a substrate, wherein said magnetic layers has vertical magnetic anisotropy and any two adjacent layers being bound by exchange force. The medium is characterized in that a fifth magnetic layer not bound by exchange force is provided over the fourth magnetic layer or that a layer made of a rare earth element/transition metal alloy in which the magnetization of rare earth elements is dominant is provided between the first and second magnetic layers which are bound together by exchange force.

Abstract: Information on a spinning magneto-optic disk is overwritten by illuminating a spot on a track on the disk with an erasing beam in the presence of a biasing magnetic field, and illuminating another spot on the same track with a writing beam during the same revolution of the disk. The erasing beam and writing beam can be focused through the same lens. The erasing beam erases all bits to the same known value, so it is not necessary to control the writing beam according to the old values of the bits. Benefits include simpler control logic and less stringent positioning requirements than in the past.