Pick-up device for magnetically recorded information and method and

Abstract

A pick-up device for reading out information which has been recorded on a magnetic medium. The device comprises a substrate and a layer of soft magnetic material overlying a surface of the substrate, the easy axis or direction of magnetization being normal to the surface and the magnetic material having properties capable of having magnetic bubble domains generated and propagated therein, so that when the pick-up device is used to read out information from a magnetic medium, patterns of magnetic domains are formed in the layer of magnetic material corresponding to the patterns of the recorded information. Although the magnetic material is of the type capable of having magnetic bubble domains generated and propagated therein, there is no need to provide the usual bias field for maintaining the bubble domains or for providing domain-transport or domain-annihilating fields. In one use of the pick-up device, light is transmitted through the substrate and through the layer of magnetic material to be reflected from a layer of light-reflective material back through the magnetic material and the substrate, whereby the polarization of the reflected light is rotated, relative to the polarization of the transmitted light, by an amount determined by the patterns of magnetic domains formed in the layer of magnetic material. Hence, the recorded information can be optically read from the magnetic medium. In another use of this device, a magnetoresistive head is disposed on the substrate, the resistance of this magnetoresistive head being varied as a function of the patterns of magnetic domains formed in the layer of magnetic material.