Seeking large thermoelectric effects in MgO-based tunnel junctions

Abstract

There is much controversy concerning thermoelectric effects in the MgO-based magnetic tunnel junctions (MTJs) as reported in some recent publications. To clarify the problem, we give calculations from atomic first-principles systemically. Large Seebeck coefficient (S) and up-limit of figure of merit (ZT) are predicted in double- and multi-barrier MTJs, with those in single-barrier MTJs being relatively small. By restraining the phonon thermal conductance through the introduction of one vacuum barrier or numbers of MgO barriers, the up-limit of ZT can be obtained. Room temperature and ZT are predicted in an asymmetric Fe MgO Fe Vaccum Fe MTJs. The resonant quantum-well states are suggested to be responsible for the enhanced thermoelectric effects in the MTJs with double- and multi-barrier.