Room temperature ferromagnetism in Sm-doped SnO2 PLD film

The effects of rare-earth-element Sm doping on the room-temperature magnetic properties of the pure SnO2 thin films fabricated by pulsed laser deposition are investigated. Only the Sm-doped SnO2 film at 600 °C exhibits ferromagnetism at room temperature. XRD and XPS measurements reveal that no magnetic impurities or second phases are present in the film. As the SnO2 thin films were prepared via laser ablation and oxygen-deficient atmosphere, a high density of oxygen vacancies and tin vacancies may be expected. Ab inito calculations on SnO2 (2 0 0) plane with LDA + USIC method indicates that the Sm dopant could have localized magnetic moment, and the introduction of nearest-neighbored oxygen vacancy to Sm dopant in the Sm-doped SnO2 (2 0 0) plane cannot only increase the magnetic moment of the system, but makes FM coupling energetically more favorable for the system. The studies demonstrate that the observed ferromagnetism in our Sm-doped SnO2 film should originate from the coexistence of the substitution of Sn4+ ions by Sm3+ ions and nearest-neighbored oxygen vacancy.