Tunneling magnetoresistance and spin-valley polarization in magnetic silicene superlattices

Abstract

We study the tunneling magnetoresistance and the spin-valley transport in silicene-based magnetic superlattices. The superlattice profile is obtained by the periodic modulation of the exchange field induced by ferromagnetic electrodes. The silicene band gap in the superlattice structure is also modulated through an external perpendicular electric field. The concept of parallel and antiparallel magnetization configurations of single magnetic junctions is extended to the periodic case by switching the magnetization orientation of the adjacent magnetic barriers in parallel and antiparallel fashion. The transfer matrix method and the Landauer-B\"uttiker formalism are used to obtain the transmission and transport properties, respectively. We find an oscillating conductance once the periodic modulation is incorporated. By tuning the external perpendicular electric field a conductance gap is obtained for the antiparallel configuration, which results in an enhancement of the tunneling magnetoresistance with respect to single magnetic junctions. In the case of the spin-valley polarization it is not possible to obtain two well-defined polarization states by simply switching the magnetization orientation, as in single magnetic junctions, due to the equivalence of the spin-valley conductance components. However, by inducing structural asymmetry in the width of barriers-wells, two well-defined polarization states can be reached. Moreover, an additional enhancement of the tunneling magnetoresistance is induced by the structural asymmetry. Our findings indicate that magnetic periodic modulation can be an option to improve the tunneling magnetoresistance and the spin-valley polarization of silicene-based structures.