Enhancement of Spin Polarization in Two-Dimensional Electron Gases at Patterned LaAlO3/SrTiO3 Interfaces

Spin-polarized two-dimensional electron gases (2DEGs) at the interfaces of SrTiO3-based correlated oxides have attracted tremendous attention in electronics and spintronics. Hitherto, the transition temperature (TC) for such spin polarization remains very low at around 20 K, seriously restricting further spin-based applications. Here, we demonstrate a new strategy to greatly enhance the spin polarization at the interfaces of the prototypical LaAlO3/SrTiO3 by conveniently inserting a SrCoO2.5-patterned Hall-bar layer. In the modified interfacial heterostructure, signatures of spin polarization, such as the Kondo effect, hysteretic magnetoresistance, magnetic hysteresis loop, and anomalous Hall effect, are all unambiguously observed. The TC of spin polarization deduced from the anomalous Hall effect is promoted to a significantly high temperature of 100 K, much higher than any reported values for 2DEGs at oxide interfaces. Combining atomic-level resolution electron energy-loss spectroscopy, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism spectroscopy, the origin of spin polarization is attributed to the occurrence of Ti3+ ions located around the interfaces. This work opens up a reliable interfacial engineering route to enhance the spin polarization in 2DEGs at oxide interfaces, which is applicable for practical spin-based logic and memory devices.