Crossover of uniaxial magnetic anisotropy direction mediated by interfacial strain of CoFe2O4 films

This study examined the deposition temperature-dependent magnetic anisotropy of CoFe2O4 films grown on Al2O3(0001) substrates using pulsed-laser deposition. X-ray diffraction revealed all films to have a 〈111〉 orientation except for the films grown at room temperature, which exhibited amorphous characteristics. Furthermore, the films deposited between 350 °C and 550 °C exhibited out-of-plane tensile strain even though, which was relieved as the deposition temperature increased. On the other hand, film deposited at 650 °C showed out-of-plane compressive strain. The in-plane and out-of-plane magnetic hysteresis loops, which were measured at room temperature, showed a decreased out-of-plane anisotropy when the deposition temperature was increased. Simple uniaxial magnetic anisotropy energy calculations based on the experimental data showed a direct correlation between the uniaxial magnetic anisotropy direction and stress of the films. X-ray photoelectron spectroscopy revealed variations in the cation distribution according to the deposition temperature.