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

Epitaxial FeCo2O4 films were grown by pulsed laser deposition on Al2O3 (0001) substrates at different growth temperatures in this work. The growth temperature directly affects the occupation of cations and the lattice constant, resulting in different magnetic phases and conductivity. The optimal growth temperature range was 450-550 degrees C. Double bandgaps were observed in the UV absorption spectra. Electrical measurements showed that the film grown at 450 degrees C had the lowest activation energy, and the structure of this film was more ordered. The magnetic analysis demonstrated that, in addition to the ferrimagnetic phase formed by the antiparallel arrangement of the tetrahedral and octahedral magnetic moments, there were two kinds of antiferromagnetic phases. One kind of antiferromagnetism was from the antiphase boundaries, and the other was localized antiferromagnetism at the octahedra formed by the Co2+ ions. The three kinds of magnetic phases showed different characteristics with changes in the growth temperature and measurement temperature.