Enhancement of thermovoltage and tunnel magneto-Seebeck effect in CoFeB-based magnetic tunnel junctions by variation of the MgAl2O4 and MgO barrier thickness

We investigate the influence of the barrier thickness of Co40Fe40B20-based magnetic tunnel junctions (MTJs) on the laser-induced tunnel magneto-Seebeck (TMS) effect. Varying the barrier thickness from 1 to 3 nm, we find a distinct maximum in the TMS effect for a 2.6-nm barrier thickness. This maximum is measured independently for two barrier materials, namely, MgAl2O4 (MAO) and MgO. Additionally, samples with a MAO barrier exhibit a high thermovoltage of more than 350 mu V in comparison to 90 mu V for the MTJs with a MgO barrier when heated with the maximum laser power of 150 mW. Our results allow for the fabrication of improved stacks when dealing with temperature differences across MTJs for future applications in spin caloritronics, the emerging research field that combines spintronics and thermoelectrics.