Copper ferrite (CuFe2O4) thin films have been prepared by rf sputtering on fused quartz and silicon (111) substrates at ambient temperature. The as-deposited film is found to be in cubic phase, which is stable only at higher temperatures in bulk. The films were annealed at temperatures ranging from 100 °C to 800 °C and slowly cooled. The films had tetragonal structure at annealing temperature above 200 °C. The c/a ratio was observed to increase with increasing annealing temperature. Transmission electron microscopy study confirmed the phase transformation from cubic to tetragonal as a function of annealing temperature. The magnetization values of the films were observed to show a maximum at the annealing temperature of 200 °C and a minimum at 500 °C. The coercivity increased monotonically from 70 Oe for the as-deposited film, to 1450 Oe for the film annealed at 800 °C. The results were explained on the basis of the phase transformation and the grain growth phenomenon.© 2002 American Institute of Physics.