Abstract: An MR head in which a spin-valve device unit is formed into a horizontal shape and an anti-ferromagnetic layer is not required, is provided. The spin-valve device unit includes a first ferromagnetic layer, one and another permanent magnetic layers arranged on both end portions of the first ferromagnetic layer and creating a magnetic path from one of the end portions of the first ferromagnetic layer toward the other thereof. A second ferromagnetic layer is provided above the first ferromagnetic layer through a non-magnetic conductive layer and a soft magnetic layer is provided above the second ferromagnetic layer through a non-magnetic layer. The both end portions of the second ferromagnetic layer are designed to contact with outer end portions of the permanent magnet layers, respectively. Surfaces of the permanent magnet layers are perpendicular to the surface of a magnetic storage medium and to the magnetization direction thereof.

Abstract: An apparatus and a method for recording, reading and erasing information, which use, as a recording medium, a magnetic film having vertical magnetic anisotropy characteristics and record, read and erase information by means of a laser beam and an external magnetic field applied to the magnetic medium. These are characterized in that the application of the external magnetic field to the recording medium is controlled by controlling the magnetic field provided by a permanent magnet put at a predetermined distance from the recording medium. For controlling the magnetic field, means for applying an external magnetic field to a recording medium is employed, which comprises a permanent magnet, a magnetic core of a high magnetic permeability material comprising a pole piece attached to at least one pole of the permanent magnet and a lag piece integrally connected to the pole piece and having a wire wound therearound, and an electric current source supplying electric current to the wire wound of the core.

Abstract: A magnetic rotary encoder for detecting incremental angular displacement, angular velocity and rotating direction using magneto-resistors is disclosed. A drum, disk or cupshaped rotary member is attachable to a rotatable shaft. A magnetic medium is provided on a surface of the rotary member and is divided at a pitch p into a plurality of magnetic sections each of which has a magnetic signal recorded. The magnetic medium produces an alternating magnetic field as the rotary member revolves. Alternatively, a plurality of permanent magnets are provided on the surface of the rotary member to produce the alternating magnetic field of the rotary member revolves. A magnetic field detector includes at least one magneto-resistor having a stripe-like configuration with width D. The magneto-resistor is located in the vicinity of the rotary member so as to be spaced from the magnetic medium or the permanent magnets by equal to or less than p at its nearest portion and by equal to or less than 20p at its furthest portion.

Abstract: A magnetic rotary encoder for detecting the absolute value of an angular displacement using magneto-resistors is disclosed. A drum, disk or cup-shaped rotary member is attachable to a rotatable shaft. A magnetic medium divided into a plurality of tracks is provided on a surface of the rotary member. Each of the tracks produces magnetic fields changing in magnitude and direction as the rotary member revolves. Alternatively, a plurality of permanent magnets are provided on the surface of the rotary member to produce the alternating magnetic field as the rotary member revolves. A plurality of magneto-resistors are provided in the vicinity of the rotating paths of the tracks and produce analog signals indicative of changes in their electrical resistances. A rotary condition detector receives the analog signals and produces digital signals and/or an analog signal indicative of the angular distance moved by the rotatable shaft in an absolute value.