Magnetic Modulation by Oxygen Vacancies in Epitaxial Ga0.5Fe1.5O3-delta

Abstract

Oxygen vacancies have often been believed to reduce ferroic properties. However, in this work, we demonstrated that oxygen vacancies caused enhanced magnetism in ferrimagnetic Ga0.5Fe1.5O3-delta by preventing Fe-O hybridization and formation of Fe2+. Epitaxial films of 001 Ga0.5Fe1.5O3-delta (GFO) were synthesized on (001) yttria-stabilized zirconia substrates by using radio-frequency magnetron sputtering, and the films were cooled in a forming gas. To see the effect of the oxygen content, we also prepared post-annealed GFO films in 500 Torr of O-2. From the analyses of the structural and the optical properties, the magnetism, and the chemical state of the two prepared samples, we verified that oxygen vacancies induced lattice expansion, reduced p-d hybridization, and importantly enhanced magnetism, i.e., increased magnetic moments and the transition temperature. Our results reveal that the superexchange interaction governing the magnetism of GFO can be controlled by the oxygen vacancy content.