Abstract: A YIG film microwave device utilizing the ferrimagnetic resonance of a YIG film, comprising a YIG film microwave element formed by a liquid phase epitaxial growth process and a photolithographic process, and a magnetic circuit including permanent magnets for applying a DC magnetic field to the YIG film microwave element. Some of the Fe.sup.3+ ions of the YIG film are substituted by nonmagnetic ions to provide the YIG film microwave device with satisfactory temperature characteristics. The YIG film microwave device is capable of operating stably over the wide range of working frequency and that of temperature.

Abstract: A region (21) having different magnetic energy from that of other portion is formed in a layer (1b) of soft magnetic material which has an easy axis of magnetization normal to the layer surface and is magnetized in one direction by applying an external bias magnetic field. By irradiating a light beam on the layer surface, a cylindrical magnetic domain b magnetized in the direction opposite to the magnetization direction is formed at a first stable position of the region (21). This cylindrical magnetic domain is moved to a second stable position by a second cylindrical magnetic domain c.multidot.b formed by the irradiation of light beam or by a temperature gradient whereby stable recording, reading thereof and accurate calculation function can be carried out.

Abstract: A thermomagnetic recording and reproducing system for use in optical magnetic disc apparatus wherein at least a first layer (1) of soft magnetic material having an easy axis of magnetization normal to the layer surface, a transparent non-magnetic intermediate layer (2), a second layer (3) of soft magnetic material having an easy axis of magnetization normal to the layer surface and a metal film or semi-metal film (4) adjacent to the second magnetized layer are superposed on one another to form a recording medium (5). In recording, a bias magnetic field is applied to the first and second magnetized layers (1) and (3) so that the magnetized layers are magnetized to have a single magnetic domain over their whole surfaces and a magnetization directed perpendicular to the layer surface.