Jahn-Teller Effect of Cu-Ferrite Films.

Copper iron oxide (CuFe2O4: Cu-ferrite) thin films were prepared on a glass substrate by vacuum evaporation and solid reaction, and annealed at 300-500°C in the air. Their crystallographic structures, magnetic properties, and electrical conductivities were investigated. The obtained films were identified by X-ray diffraction analysis as Cu-ferrite films of a tetragonal system with an axial ratio (c/a) of 1.507. The saturation magnetization 4 πMs, coercive force Hc, and Curie temperature Tc were 2.4 kG, 420 Oe, and 460°C, respectively. The temperature dependence of the magnetization and conductivity for the films showed remarkable changes at 360°C, which were considered to be caused by dislocation of the crystal structure due to the Jahn-Teller effect.