Effect of Oxygen Vacancies on Ferromagnetism of Cu-Doped BaSnO3

As a cubic perovskite structure material with a wide bandgap of 3.1 eV, BaSnO3 has various functional applications due to its excellent light transmission, electric conductivity, and heat resistance. By doping with a small amount of transition, metal ions may further introduce ferromagnetism in BaSnO3 and extend its functions to spintronics. In this work, 5% Cu ions (atomic ratio) have been doped into BaSnO3 (Ba0.95Cu0.05SnO3) prepared by solid state reaction, which is further annealed in argon or oxygen atmosphere to obtain different concentrations of oxygen vacancies. Clear room temperature ferromagnetism with saturated magnetization of about 0.0025 emu/g has been observed in the as-prepared Cu-doped BaSnO3, which is strongly suppressed after annealing in both argon and oxygen conditions. First-principles calculations suggest that the magnetic properties of Cu-doped BaSnO3 may come from the ferromagnetic Cu clusters embedding in BaSnO3. In addition, oxygen vacancies in the appropriate position help to strengthen the ferromagnetic coupling between adjacent Cu ions. Our results clearly demonstrate the fine tuning of oxygen vacancies, not only concentration, but also locations, may significantly influence the magnetic states of Cu-doped BaSnO3.