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

We study spin-dependent valley currents and magnetoresistance (TMR) in double magnetic layer graphene-based N/F1/St/F2/N junction where N, F1,2 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, Ik↑, Ik↓, Ik′↑ and Ik′↓, 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.