Ferrite Thin Films

Abstract

Thin films of ferrites of various compositions have been prepared. Two methods have been developed, both involving a spray technique whereby hot suspensions of hydroxides are directed onto a heated substrate. The ferrite films are formed essentially through a coprecipitation mechanism. X-ray diffraction has shown that the films have a cubic spinel structure. Various compositions have been attained; magnetite, nickel ferrous ferrite, a magnetite-zinc ferrite series, and other mixed ferrites. Coercive force measurements were made from hysteresis loops obtained on a 1000-cycle loop tracer. The films are magnetically isotropic and have a high squareness ratio. Film thicknesses have been varied from a few hundred A to about 1 μ. Relative film thicknesses were estimated by using a spectrophotometric technique. For a fixed composition, coercive force decreases with increasing thickness. Magnetite films had coercive forces varying from 170 to 300 oe depending on thickness. A nickel ferrous ferrite series had coercive forces varying from 225 oe for thick films to 400 oe for a very thin one. Coercive force measurements are related to composition variations in a series of zinc ferrous ferrite films.