Tunable bandgap and ferromagnetism in sputtered epitaxial Sn1-xMgxO2 thin films

摘要

Room-temperature magnetic behavior and tunable bandgap of epitaxial Sn1-xMgxO2 films were investigated. The Mg dopants can enhance the ferromagnetism and the largest saturation magnetization of 7.0 emu/cm3 has been observed in Sn0.94Mg0.06O2 film which has the narrowest bandgap. The ferromagnetism decreases with further doping but increases in Sn0.84Mg0.16O2 film after air annealing at 700 °C. The ferromagnetism is likely due to the double exchange mechanism through the p-p interaction. Mg interstitials can irreversibly transform to Mg substitutions by thermal treatment. The generated oxide alloys will decrease the optical bandgap and ferromagnetism of the samples.