Enhancement of thermovoltage and tunnel magneto-Seebeck effect in CoFeB based magnetic tunnel junctions by variation of the MgAl$_2$O$_4$ and MgO barrier thickness

摘要

We investigate the influence of the barrier thickness ofCo$_{40}$Fe$_{40}$B$_{20}$ based magnetic tunnel junctions on the laser-inducedtunnel magneto-Seebeck effect. Varying the barrier thickness from 1nm to 3nm,we find a distinct maximum in the tunnel magneto-Seebeck effect for 2.6nmbarrier thickness. This maximum is independently measured for two barriermaterials, namely MgAl$_2$O$_4$ and MgO. Additionally, samples with anMgAl$_2$O$_4$ barrier exhibit a high thermovoltage of more than 350$\mu$V incomparison to 90$\mu$V for the MTJs with MgO barrier when heated with themaximum laser power of 150mW. Our results allow for the fabrication of improvedstacks when dealing with temperature differences across magnetic tunneljunctions for future applications in spin caloritronics, the emerging researchfield that combines spintronics and themoelectrics.