Oxygen vacancies induced ferromagnetic behaviors in Co3O4–δ: An experimental and first-principles study

Highlights: •Epitaxial Co₃O_4-δ films were prepared. •Magnetic properties of Co₃O_4-δ were investigated. •Ferromagnetism in Co₃O_4-δ is related to oxygen vacancies. -- Abstract: The structural and magnetic properties of Co₃O_4-δ were investigated by both first-principles and experimental studies. The results of first-principles calculations indicate that the spin splitting induced by oxygen vacancies can lead to the net moment in the Co₃O_3.875. The density of states of Co₃O₄ shows a band gap of 2.2 eV, while the impurity states appear with the oxygen vacancies. Furthermore, the Co₃O_4-δ films with oxygen vacancies were grown on MgAl₂O₄ and SrTiO₃ substrates by using reactive sputtering. The structural analysis reveals that the Co₃O_4-δ films are epitaxial. Consistent with the first-principles study, magnetism is observed in the Co₃O_4-δ films, which attributes to the oxygen vacancies influencing spin structure by superexchange interaction.