Ferromagnetism and spin-dependent transport at a complex oxide interface

Complex oxide interfaces are a promising platform for studying a wide array of correlated electron phenomena in low dimensions, including magnetism and superconductivity. The microscopic origin of these phenomena in complex oxide interfaces remains an open question. Here we investigate the magnetic properties of semi-insulating NdTiO3/SrTiO3 (NTO/STO) interfaces and present the first millikelvin study of NTO/STO. The magnetoresistance (MR) reveals signatures of local ferromagnetic order and of spin-dependent thermally activated transport, which are described quantitatively by a simple phenomenological model. We discuss possible origins of the interfacial ferromagnetism. In addition, the MR also shows transient hysteretic features on a time scale of ∼10-100s. We demonstrate that these are consistent with an extrinsic magnetothermal origin, which may have been misinterpreted in previous reports of magnetism in STO-based oxide interfaces. The existence of these two MR regimes (steady-state and transient) highlights the importance of time-dependent measurements for distinguishing signatures of ferromagnetism from other effects that can produce hysteresis at low temperatures.