Growth and magnetic properties of CoCr2O4 epitaxial films

Epitaxial spinel CoCr2O4 (CCO) thin films have been grown by rf magnetron sputtering on rocksalt MgO and spinel MgAl2O4 substrates. Structural and magnetic properties have been investigated as a function of either the film thickness (above 30 nm) or the deposition temperature. All the films, on each type of substrate, are structurally relaxed. However, significant differences have been observed on the magnetic properties. Whereas CCO films grown on MgAl2O4 display ferromagnetic properties comparable to those of the bulk material, the films grown on MgO have a much reduced magnetization. Comparison of the properties of films grown at different temperatures suggests that the Mg diffusion from the substrate is likely the origin of the depressed magnetic properties of films grown on MgO. These findings indicate that MgO is not as suitable as MgAl2O4 as template for CCO growth.