Strong spin-orbit coupling and magnetism in (111) (La0.3Sr0.7)(Al0.65Ta0.35)O-3/SrTiO3

Abstract

Two-dimensional conducting interfaces in SrTiO3-based heterostructures display a variety of coexisting and competing physical phenomena, which can be tuned by the application of a gate voltage. (111) oriented heterostructures have recently gained attention due to the possibility of finding exotic physics in these systems due to their hexagonal surface crystal symmetry. In this work, we use magnetoresistance to study the evolution of spin-orbit interaction and magnetism in (111) oriented (La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3. At more positive values of the gate voltage, which correspond to high carrier densities, we find that transport is multiband, and dominated by high-mobility carriers with a tendency toward weak localization. At more negative gate voltages, the carrier density is reduced, the high-mobility bands are depopulated, and weak antilocalization effects begin to dominate, indicating that spin-orbit interaction becomes stronger. At millikelvin temperatures, at gate voltages corresponding to the strong spin-orbit regime, we observe hysteresis in magnetoresistance, indicative of ferromagnetism in the system. Our results suggest that in the (111) (La0.3Sr0.7)(Al0.65Ta0.35)O3/SrTiO3 system, low-mobility carriers that experience strong spin-orbit interactions participate in creating magnetic order in the system. © 2018 American Physical Society.