CuFe2O4 thin films: Elaboration process, microstructural and magneto-optical properties

Thin films of CuFe2O4 tetragonally distorted spinel ferrite were deposited by r.f. magnetron sputtering from a sintered target of the same composition in argon gas atmosphere. It was shown that traces of water in the sputtering chamber could affect the crystalline orientation of samples annealed at 450 degrees C. In fact, traces of water favour the formation of [310] oriented films, The as-sputtered samples were made of very small crystallites (less than 10 MI in diameter). The films annealed at 450 degrees C had crystallites of 20-30 nm diameter at their upper surface. No significant differences were apparent between the microstructures of the annealed films despite their differing crystalline orientations. In contrast, the highest coercivities and Faraday rotations were measured for the [310] oriented samples. The deposited films were single-phase CuFe2O4 during the first 20 h sputtering. After this time, as well as the ferrite, another phase, CuFeO2, was revealed by X-ray diffraction, Sputtering of the target by oxygen allowed recovery of a pure ferrite phase on the deposited films.