| 摘要 |
<p>1382977 Magnetic storage devices PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 9 May 1973 [12 May 1972] 22081/73 Heading H3B A ferrite storage layer 2 mounted on a transparent substrate 1, and intended for use in a magneto-optical store, has its individual storage positions separated by discontinuities in the storage material, and has a non-ferromagnetic surface overlay which exerts a tensile stress on the surface of the storage layer and in its plane. The discontinuities may be provided by grooves 4 extending partially or wholly through the layer or by grain boundaries formed by a sintering process. The layer is prepared by surface grinding and polishing, followed by ion etching to remove cystallographic defects and stresses. A layer 3 of a transparent resin adhesive is used to secure the storage layer to the substrate. The grooves may be produced by conventional photolithographic methods, or by using an energy ray deflected in a controlled manner, preferably by the optical control system used in the magneto-optical store. A further method which produces random discontinuities involves heating the layer so that separations are caused by the different coefficients of thermal expansion of the magnetic layer and the substrate. The grooved layer is overlaid by a vacuum-deposited layer of silica 5 which provides mechanical support, stabilizes the preferred direction of magnetization, and prevents both surface reflection of an incident optical beam and scattering by the groove walls. The magnetic layer may consist of Gd 3 Fe 5 O 12 , and its magnetic state normal to its plane may be changed by the combination of an external bias field of appropriate direction and a light beam of sufficient intensity to raise the temperature of a selected storage portion to the Curie or compensation point. Reading is by the magneto-optical Faraday effect.</p> |
