Direct\nObservation of Room-Temperature Stable Magnetism in LaAlO₃/SrTiO₃ Heterostructures

Abstract

Along with an unexpected conducting interface between nonmagnetic insulating perovskites LaAlO₃ and SrTiO₃ (LaAlO₃/SrTiO₃), striking\ninterfacial magnetisms have been observed in LaAlO₃/SrTiO₃ heterostructures. Interestingly, the strength of the interfacial\nmagnetic moment is found to be dependent on oxygen partial pressures\nduring the growth process. This raises an important, fundamental question\non the origin of these remarkable interfacial magnetic orderings.\nHere, we report a direct evidence of room-temperature stable magnetism\nin a LaAlO₃/SrTiO₃ heterostructure prepared\nat high oxygen partial pressure by using element-specific soft X-ray\nmagnetic circular dichroism at both Ti L_3,2 and O K edges.\nBy combining X-ray absorption spectroscopy at both Ti L_3,2 and O K edges and first-principles calculations, we qualitatively\nascribe that this strong magnetic ordering with dominant interfacial\nTi³⁺ character is due to the coexistence of LaAlO₃ surface oxygen vacancies and interfacial (Ti_Al–Al_Ti) antisite defects. On the basis of this new understanding,\nwe revisit the origin of the weak magnetism in LaAlO₃/SrTiO₃ heterostructures prepared at low oxygen partial pressures.\nOur calculations show that LaAlO₃ surface oxygen vacancies\nare responsible for the weak magnetism at the interface. Our result\nprovides direct evidence on the presence of room-temperature stable magnetism and a novel perspective\nto understand magnetic and electronic reconstructions at such strategic\noxide interfaces.