Strain-induced switching of magnetoresistance and perfect spin-valley filtering in graphene

Abstract

We study spin-dependent valley currents and magnetoresistance (TMR) in double magnetic layer graphene-based N/ F 1/St/ F 2/ N junction where N, F 1,2 and St are normal, ferromagnetic and strain-engineered graphene, respectively. Local strain in the St region causes a pseudo-vector potential with the same magnitude for the K- and K′-valleys but different sign, leading to valley polarization when applying real vector potential into the junction. The F layers cause the Zeeman field for controlling spin current and can be orientated either parallel ( P) or anti parallel ( AP). As an effect of the interplay of the Zeeman field and the strain field, the current in the junction is split into four current groups, I k↑ , I k↓ , I k′↑ and I k′↓ , called spin-valley currents. We find that, the interplay of the Zeeman and strain field causes a perfect spin-valley filtering in the angular space only for the P configuration. Large TMR and switching of TMR triggered by a very small strain are also predicted. Our work reveals the potential of the interplay of the Zeeman and the strain field for application of spin-valley-based nanoelectronics and the switching effect induced by a very small strain should be applicable for strain sensor device.