公开(公告)号：DE1524875A1

公开(公告)日：1970-10-22

申请号：DEJ0034948

申请日：1967-11-02

Applicant: IBM

Inventor： DENIS MEE CHARLES ,  EDWARD MAC DONALD RONALD ,  VOEGELI OTTO

IPC: G11B11/105 ,  G11C11/14

Abstract: 1,133,919. Magneto-optical data storage. INTERNATIONAL BUSINESS MACHINES CORP. 19 Oct., 1967 [10 Nov., 1966], No. 47554/67. Heading H3B. Data stored in a magnetic garnet thin film is read by directing a beam of polarized light, having a wavelength less than 5000 A, on to the storage location and detecting changes in the polarization of the beam caused by the stored data. The film preferably consists of gadolinium iron garnet, less than 2 microns thick, and preferably 0À2 micron thick, mounted on a transparent substrate. The film is maintained at its compensation temperature in a magnetic field which is incapable of switching the magnetization direction of any part of the film at the compensation temperature. To store data polarized light, e.g. from a zinc oxide laser or from a gallium arsenide laser associated with a frequency doubler, is directed on to a selected region of the film by means of an optical deflector, and raises the temperature of this region. The magnetic field is then sufficient to switch the magnetization in this region to store a " 1," for example. If a " 0 " is to be stored either the light beam or the magnetic field is suppressed, or the field is reversed. During read out the magnetic field is switched off and the film is scanned more rapidly to reduce to heating of the storage sites. The reading process may utilize either the Faraday effect, whereby the plane of polarization of the beam is rotated, or the circular dichroism of the film, whereby one of the circularly polarized components of the incident beam is absorbed more than the other, depending on the direction of the remanent magnetization in the storage region.