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A two-dimensional electron gas (2DEG) formed at LaAlO3/SrTiO3 (LAO/STO) interfaces, which consists of itinerant d-orbital electrons, has been observed a lot of attractive physics, such as ferromagnetism, superconductivity and even their coexistence. The ability of d-electron 2DEG for spintronics has been also demonstrated as a high-efficient spin-charge conversion via the Rashba field and theoretical estimations of a long spin lifetime, so that a spintronics application of d-electron 2DEGs is one of the hottest issues in the oxide physics. Here, we demonstrate room-temperature spin transport at LAO/STO interfaces.
We fabricated NiFe (Py) and Pt or Ta wires, separated by less than 1 micron, on LAO/STO substrate (5 unit cells in LAO-layer thickness). Spins are injected from the Py wire into the LAO/STO interface by excitation of the ferromagnetic resonance (FMR) of the Py (spin pumping). The spin current through the LAO/STO interface can be detected as an electromotive force (EMF) by the inverse spin Hall effect (ISHE) from the non-local nonmagnetic wire. We successfully observed the electromotive force from the Pt under the FMR. The EMF has symmetric and asymmetric line shape. The symmetric part is attributed to the EMF of the ISHE (VISHE). In particular, the sign of the VISHE was reversed by inverting the direction of the external magnetic field and by switching detector material from Pt to Ta, where the latter possess a negative spin Hall angle. These results strongly support the notion that over 100 nm spin propagation in the 2DEG indeed has been successfully achieved.
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