Oxygen-defect-dependent ferromagnetism and strain modulation in free-standing two-dimensional TiO2 monolayers

Abstract

Recently, layered two-dimensional titania (2D-TiO₂) with a reduced band gap has been successfully synthesized. However, as an important application in spintronics, ferromagnetism in this material has not been investigated so far. To obtain the expected ferromagnetism, the formation and stability of the most prominent oxygen defects in a TiO₂ monolayer under different external strains were explored systematically. The calculated results disclosed that structural deformation induced by tensile strain not only led to changes in the oxygen defect formation energy but also modified its magnetic features. With an increase in compressed strain, the Curie temperature in this system decreased due to insufficient spin polarization. Our calculations provide a strategy to utilize oxygen defect and strain engineering to realize applications of 2D TiO₂ monolayers in spintronics.