Spin polarized transport in an asymmetric ferromagnetic/quantum dot/ferromagnetic system

Abstract

We investigate the tunnel magnetoresistance (TMR) of the double barrier magnetic tunnel junction, where a quantum dot (QD) with discrete electron and hole energy levels is sandwiched between ferromagnetic leads. The effects of the symmetry of the coupling between the leads and the dot on both the TMR and spin accumulation (SA) are studied for voltage ranges corresponding to the QD’s single and double occupancies. When the QD is singly occupied, both the TMR and SA assume at their minimum values for symmetrical junctions with identical coupling strengths. For the doubly occupied QD, the opposite occurs with the highest TMR and SA being observed for symmetrical junctions with identical coupling strengths. The TMR is found to be strongly correlated with the spin accumulation in the QD.