Evolution of the magnetoresistance lineshape with temperature and electric field across Nb-doped SrTiO3 interface

Abstract

We report on the temperature and electric field driven evolution of the magnetoresistance lineshape at an interface between Ni/AlOx and Nb-doped SrTiO3. This is manifested as a superposition of the Lorentzian lineshape due to spin accumulation and a parabolic background related to tunneling anisotropic magnetoresistance (TAMR). The characteristic Lorentzian line shape of the spin voltage is retrieved only at low temperatures and large positive applied bias. This is caused by the reduction of the electric field at large positive applied bias which results in a simultaneous reduction of the background TAMR and a sharp enhancement in spin injection. Such mechanisms to tune magnetoresistance are uncommon in conventional semiconductors.