Giant crystalline anisotropic magnetoresistance in nonmagnetic perovskite oxide heterostructures

摘要

Anisotropic magnetoresistance (AMR) was observed by Lord Kelvin one-and-half centuries ago in iron and nickel. The resistance of these ferromagnetic conductors showed a few percent change when a magnetic field was applied along or across the current. Subsequently, a 20% AMR was demonstrated in alloys of nickel and iron (permalloys). Efforts have then been devoted to extend this effect in multifunctional materials. The oxide heterostructure exhibiting two-dimensional electron liquid is one of the potential candidates as it has shown to exhibit emergent magnetic ordering, strong spin-orbit interactions, and anisotropic magnetoresistance. Here we show a giant crystalline AMR as large as 57% to 104% in anisotropic quantum wells based on nonmagnetic perovskite oxides LaAlO_3 and SrTiO_3, providing an alternative way in tailoring AMR with an extremely large effect. The AMR maximum appears when the magnetic field points along the in-plane [110] direction, irrespective of the direction of current flow, which is consistent with the idea of crystalline AMR. Data analysis and density functional theory calculation show that the observed giant crystalline AMR mainly originates from the strong anisotropic spin-orbit field at the interface due to its unique elliptical Fermi surface related to its orbital configuration and reconstruction. This work demonstrates that perovskite oxide interface is a unique platform for orbital physics.