Nippon Telegraph and Telephone Public Corporation

Nippon Telegraph and Telephone Corporation

Iwao Hatakeyama

Osamu Ishii

Fumikatsu Yoshimura

Tetsuo Iijima

Shizuka Yoshii

Koutarou Nonaka

Yasushi Maeda

An overwritable magneto-optic recording system has a recording medium with a substrate, a recording magnetic film and a reproducing magnetic film deposited on the substrate. The reproducing magnetic film has a Curie temperature lower than that of the recording magnetic film, and coercive force Hc higher than that of the recording magnetic film. In a write process, a magnetic head writes data magnetically on the recording magnetic film, then, in a transfer process, an optical head (which is positioned downstream along the relative movement of the recording medium and the optical head) heats the recording medium higher than the Curie temperature of the reproducing magnetic film so that the reproducing magnetic film loses its magnetic property. During the cooling period after heating, recorded bits in the recording magnetic film are transferred to the reproducing magnetic film which restores its magnetic property. In the reproducing process, the optical head irradiates the reproducing magnetic film by a polarized coherent beam, and the data is reproduced on the principle that the polarization of the reflected beam depends upon the recorded data based on the Kerr effect. Thus, the high speed recording defined by a magnetic recording, and high density recording defined by an optical recording are obtained. Overwrite is possible merely by writing data by the magnetic head as in the case of the write process.

Magneto-optic recording system with overwrite capability

.gamma.-Fe.sub.2 O.sub.3 film added at least one selected from the group consisting of Pd, Au, Pt, Rh, Ag, Ru, Ir, Os as additive, especially Os are disclosed. Reduction from .alpha.-Fe.sub.2 O.sub.3 to Fe.sub.3 O.sub.4 is accelerated by additive Os to accompany to a uniform reduction and increased the ratio of magnetic phase in the film. .gamma.-Fe.sub.2 O.sub.3 film medium added Os improves the saturation magnetization and increases the coercive force in proportion to amount of additive Os. Application of an external field to said film introduced magnetic anisotropy into said film, therefore said film medium improves coercive force and squareness of hysteresis loop by the grant of anisotropy. .gamma.-Fe.sub.2 O.sub.3 crystal grain is prepared by additive Os to obtained fine grain. The resultant .gamma.-Fe.sub.2 O.sub.3 film medium decreases the noise.

Iron oxide magnetic film and process for fabrication thereof

A magnetic head for digital signal recording/reproducing (FIG. 11) having a C-ring shaped core (11.1) with a gap (G) for introducing leakage flux of a recording medium, a conductor (11.2, Y) for generating bias flux in hard magnetization axis of the core (11.1), apparatus (10.3, 11.3) for illuminating the core (11.1) with polarized optical beam, apparatus (11.4) for analyzing beam reflected by the core to convert polarization rotation to optical strength, and photo-detector (12.5) for providing electrical output signal relating to optical strength. The core is small enough to have a single magnetic domain, and is magnetized in the whole area because of the presence of the bias flux in spite of weak leakage signal flux, thus, the core has the capability to amplify signal flux, thus, the present head has high sensitivity and is capable of detecting flux in small area to be used for high density recording higher than 8000 bits/mm.

High density magnetic head

.gamma.-Fe.sub.2 O.sub.3 film with at least one additive selected from the group consisting of Pd, Au, Pt, Rh, Ag, Ru, Ir, and Os, especially Os are disclosed. Reduction from .alpha.-Fe.sub.2 O.sub.3 to Fe.sub.3 O.sub.4 is accelerated by additive Os to achieve a uniform reduction and increase the ratio of magnetic phase in the film. .gamma.-Fe.sub.2 O.sub.3 film medium with Os improved saturation magnetization and increased coercive force in proportion to amount of additive Os. Application of an external field to said film introduces magnetic anisotropy into said film, therefore said film medium improves coercive force and squareness of hysteresis loop by the introduction of anisotropy. .gamma.-Fe.sub.2 O.sub.3 crystal grain is prepared by additive Os to obtain fine grain. The resultant .gamma.-Fe.sub.2 O.sub.3 film medium a decreased noise level.

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Mito, Japan

Iwao Hatakeyama