Enhancement of Thermopower by Structural Asymmetry in Double-Barrier Tunnel Junctions

Thermopower is studied in double-barrier magnetic tunnel junctions (DBMTJs) with a non-magnetic metal (NM) spacer by considering structural asymmetry—related to the different thicknesses of the MgO insulators—in the linear response regime. Using non-equilibrium Green’s function (NEGF) formalism, it is found that the thermopower is larger in the case with thicker left insulator than the other cases which is related to the voltage drop within the insulator layer. The thermopower has shown its maximum value as large as S = 482μ V/K in the anti-parallel configuration of the magnetizations and T = 300K. Therefore, it is possible to achieve the large thermopower in the thermoelectric devices based on MTJs.