PROCESS FOR PREPARING A GARNET FILM

摘要

1,262,039. Light modulators; magnetooptical data storage. INTERNATIONAL BUSINESS MACHINES CORP. 17 Nov., 1970 [22 Dec., 1969], No. 54517/70. Headings H3B and H4F. [Also in Divisions C1 and H1] A magneto-optic device comprises a crack-free garnet film of formula Gd 3-x Tb x Fe 5 O 12 (x=0-0À75) on a substrate of glass having a thermal expansion coefficient of 85-105 Î 10-7 and an annealing temperature above 750‹ C. The glass may be a barium-titanium-silicate glass, the garnet film is built up from successive depositions of mixed oxides which are heated to form crystalline garnet (see Division C1). In examples, a sample Gd 3 Fe 5 O 12 film is made. It is tested on a magneto-optic recording and read out device by fixing the sample to the edge of a disc rotating, in a temperature-controlled chamber, through a laser beam. The beam passes through apertures in the polepieces of an electromagnet arranged so that the sample film is simultanously subjected to illumination and a magnetic field.