Magneto-optical information storage device using photoconductive control element

Abstract

The invention relates to a device for magneto-optic memories controlled by light and/or heat in an external magnetic field, in which the magneto-optic material of the memory has a photoconductive layer which can be activated by the control beam and which can be controlled by means of electrodes provided thereon via a current or voltage source.

What is claimed is: 
     
       1. .[.An.]. .Iadd.In an .Iaddend.information storage .Iadd.and retrieval .Iaddend.device comprising .[.a.]. .Iadd.an information .Iaddend.storage plate of .[.a magnetizable.]. .Iadd.magneto-optic .Iaddend.material, .[.means including a light beam.]. .Iadd.means for heating selected area of said storage plate, means to produce a magnetic field to effect storage within one of the heated areas of a value represented by one of two stable orientations, and means utilizing a magneto-optical effect .Iaddend.for .[.recording and.]. retrieving information .[.in.]. .Iadd.from .Iaddend.said storage plate, .Iadd.the improvement comprising .Iaddend.a photoconductive layer on the magneto-optic material of the storage plate, and electrode means on said photoconductive layer, .Iadd.said heating means including the combination of optical means for positioning a spot of activating radiation on said photoconductive layer whereby a selected area of said photoconductive layer is rendered electrically conductive, .Iaddend.said electrode means being connected to an electrical power source .[.to heat said layer.]. .Iadd.whereby a current can flow within said selected area and thermal energy is dissipated in said area which heats an adjacent area of the storage plate .Iaddend. . 
     
     
       2. A device as claimed in claim 1, wherein the electrodes are transparent and the photoconductive layer is disposed between the transport electrodes. 
     
     
       3. A device as claimed in claim 1, wherein the electrodes are positioned only on one surface of the photoconductive layer. 
     
     
       4. A device as claimed in claim 1 wherein the magneto-optic material is iron garnet having a domain formation. 
     
     
       5. A device as claimed in claim 1 wherein the photoconductive layer is transparent. 
     
     
       6. A device as claimed in claim 1 wherein the photoconductive layer is not transparent and the surface of the magneto-optic material remote from the photoconductive layer is reflecting. 
     
     
       7. A device as claimed in claim 3 wherein the electrodes are positioned on a surface of the photoconductive layer facing the magneto-optic material. 
     
     
       8. A device as claimed in claim 1 wherein the photoconductive layer is cadmium sulfide. 
     
     
       9. A device as claimed in claim 4 wherein said magneto-optic material is a bismuth substituted ferrimagnetic garnet. 
     
     
       10. A device as claimed in claim 1 wherein said .[.light beam.]. .Iadd.optical means .Iaddend.is a laser beam.