CHEMICAL MODIFICATION OF MAGNETOOPTIC GARNET FILM PROPERTIES

Single-crystal magneto-optic garnet films of composition (BiTm)3(FeGa) 5012 have applications to spatial light modulators, optical isolators, and magnetic-field sensors. These as-grown films have a coercivity un der 1 Oe and can support cm-size stable domains. It has been found tha t chemical treatments with oxidizing or reducing gases can reversibly modify the magnetic properties. Treatments are performed at 400-700-de grees-C for fixed times. Reducing treatments dilate the x-ray lattice constant up to 0.1%, introduce Fe2+ monitored by increased optical abs orption at 1.00-1.06 pm and decrease Faraday rotation about 5% over th e visible spectrum. Oxidation can partially or totally reverse these p arameters. Magnetic measurements on the bulk film show that coercivity can be finely controlled, square hysteresis loops attained, and domai n-wall mobility changed. At the same time the initial perpendicular an isotropy H(k) Of 8-12 kOe is decreased while the saturation magnetizat ion (4piM(s)) of 100-150 G is affected to a minor degree. For magneto- optic imaging of defects, the resolution, contrast, and device operati on are assisted favorably. Magnetic measurements are presented as a fu nction of specific chemical treatment. The data suggest that an oxygen vacancy mechanism is operative at the film surface layers.