Magnetic properties of CoFe2O4 thin films prepared by a sol-gel method

Abstract

Thin films with cobalt ferrite layers on thermally oxidized silicon wafers were fabricated by a sol-gel method. Magnetic and structural properties of the films were investigated with an x-ray diffractometer, a vibrating sample magnetometer and atomic force microscopy. The crystallization temperature for Co ferrite thin films was determined by using Mossbauer spectroscopy. Co ferrite films annealed at and above 450 degrees C have only a single phase spinel structure without any preferred crystallite orientation. Their rms surface roughness is less than nm and the size of grains is about 30 nm for annealing temperatures greater than 650 degrees C, Films fired at and above 550 degrees C have moderate saturation magnetization and there is no significant difference of their magnetic properties for external fields applied parallel and perpendicular to their planes. The coercivity shows a strong dependence on the annealing temperature. (C) 1998 American Institute of Physics. [S0021-8979(98)02417-7]