Evolution of the magnetoresistance lineshape with temperature and electric field across Nb-doped SrTiO$_3$ interface

TL;DR

This study investigates how temperature and electric field influence the magnetoresistance lineshape at a Ni/AlO$_x$ and Nb-doped SrTiO$_3$ interface, revealing mechanisms to tune spin injection and magnetoresistance.

Contribution

It demonstrates the temperature and electric field dependence of the magnetoresistance lineshape, highlighting the interplay between spin accumulation and TAMR at the interface.

Findings

Lorentzian lineshape appears only at low temperatures and high positive bias.

Electric field reduction at positive bias enhances spin injection.

Magnetoresistance tuning mechanisms differ from conventional semiconductors.

Abstract

We report on the temperature and electric field driven evolution of the magnetoresistance lineshape at an interface between Ni/AlO$_x$ and Nb-doped SrTiO$_3$. 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 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.