Pristine SnO2 thin films: origins of high Curie temperature

Abstract We investigate the origin of ferromagnetism (FM) and the exceptionally high Curie temperature ( T C ) in undoped SnO 2 films. Ultra-thin SnO 2 films were found to exhibit significant FM, while thicker films show a diamagnetic behavior. Structural and chemical analyses reveal a variation in oxygen vacancy concentrations between thin and thick films. Notably, an exceptionally high T C exceeding 800 K is observed for the first time. XPS and XAS analyses reveal the presence of oxygen and tin vacancies, which might play a crucial role in the observed magnetism. Theoretically, it was supposed that oxygen vacancies play a crucial role in the FM of SnO 2 films. However, the experimentally observed T C surpasses the predicted 505 K, suggesting additional contributing factors. This suggests that both oxygen and tin defects might contribute to the total magnetic moment. The findings highlight the key role of defect-induced magnetism in SnO 2 thin films and provide insights into the fundamental mechanism driving high- T C FM in undoped oxide semiconductors.