Magnetic two-dimensional electron gases with high Curie temperatures at LaAlO_3/SrTiO_3:Fe interfaces

摘要

Spin-polarized two-dimensional electron gas (2DEG) at the interface of two insulating perovskite oxides has been a focus of intensive studies in recent years. So far all attempts to construct magnetic 2DEG are based on the selection of an appropriate buffer layer or cap layer in SrTiO_3-based heterostructures, and the magnetic effect thus produced on 2DEG is indirect and weak. Here, we fabricated the 2DEG based on Fe-doped SrTiO_3 that is superparamagnetic rather than diamagnetic like SrTiO_3. In addition to good metallicity, considerable Kondo effect, and negative magnetoresistance, the most striking observation of the present work is the occurrence of the anomalous Hall effect up to room temperature. This is transport evidence for the existence of spin-polarized 2DEG at high temperatures. As suggested by the monotonic increase of Curie temperature with carrier density, the magnetic exchange between magnetic ions could be mediated by the itinerant electrons of the 2DEG. The present work opens an avenue for the exploration of spin-polarized 2DEG.