Ferromagnetism in pseudocubic BaFeO3 epitaxial films

Growth and properties of epitaxial BaFeO3 thin films in the metastable cubic perovskite phase are examined. BaFeO3 films were grown on (012) LaAlO3 and (001) SrTiO3 single crystal substrates by pulsed-laser deposition. X-ray diffraction shows that films grown between 650 and 850°C yield an oxygen-deficient BaFeO2.5+x pseudocubic perovskite phase that decreases in lattice spacing with increasing growth temperature. Magnetization measurements on as-deposited BaFeO3 films indicate weakly ferromagnetic behavior. Annealing in 1atm oxygen ambient converts them into conductive and robustly ferromagnetic pseudocubic BaFeO3 phase with TC=235K. Observation of ferromagnetism with increasing oxygen content is consistent with superexchange coupling of Fe+4–O–Fe+4.