Polarity-tunable magnetic tunnel junctions based on ferromagnetism at oxide heterointerfaces

Abstract

Complex oxide systems have attracted considerable attention because of their fascinating properties, including the magnetic ordering at the conducting interface between two band insulators, such as LaAlO 3 and SrTiO 3. However, the manipulation of the spin degree of freedom at the LaAlO 3 /SrTiO 3 heterointerface has remained elusive. Here, we have fabricated hybrid magnetic tunnel junctions consisting of Co and LaAlO 3 /SrTiO 3 ferromagnets with the insertion of a Ti layer in between, which clearly exhibit magnetic switching and the tunnelling magnetoresistance effect below 10 K. The magnitude and sign of the tunnelling magnetoresistance are strongly dependent on the direction of the rotational magnetic field parallel to the LaAlO 3 /SrTiO 3 plane, which is attributed to a strong Rashba-type spin-orbit coupling in the LaAlO 3 /SrTiO 3 heterostructure. Our study provides a further support for the existence of the macroscopic ferromagnetism at LaAlO 3 /SrTiO 3 heterointerfaces and opens a novel route to realize interfacial spintronics devices.