Cobalt ferrite films CoxFe3-xO4 (x = 0.3-1.0) of spinel structure with different textures were prepared by rf sputtering. Annealing in a temperature range from 400 to 600 degrees C led to different changes in the texture and magnetic properties. Peaks at 740 nm in Faraday rotation spectra increased with annealing temperature in different ways for different Co composition.