Regulation of growth temperature on structure, magnetism of epitaxial FeCo2O4 films

Epitaxial FeCo2O4 films were grown by pulsed laser deposition on Al2O3 (0001) substrate at different growth temperatures. The growth temperature directly affects the occupation of cations and lattice constant, resulting in different magnetic phases and conductivity. The optimal growth temperature range is 450-550oC. Double band gaps were observed in UV absorption spectra. Electrical measurement shows that the film grown at 450oC has the lowest activation energy, and the structure of the film is more ordered. Magnetic analysis demonstrates that in addition to the antiparallel arrangement of tetrahedral and octahedral magnetic moments forming a ferrimagnetic phase, there are two kinds of antiferromagnetic phases. One kind of antiferromagnetism is from antiphase boundaries, and the other is a localized antiferromagnetism at octahedrons formed by the Co2+ ions. The three kinds of magnetic phases show different characters with the change of growth temperature and measurement temperature.