[10a-M101-9~12] 10.2 Fundamental and exploratory device technologies for spin

▼ [10a-M101-10] First-principles calculation of Seebeck coefficients for Fe/MgO/Fe and Fe/MgAl₂O₄/Fe magnetic tunneling junctions

〇Kaoru Yamamoto¹, Keisuke Masuda¹, Ken-ichi Uchida^1,2,3, Yoshio Miura¹ (1.NIMS, 2.The Univ. of Tokyo, 3.CSRN Tohoku Univ.)

Keywords:tunnel magneto-Seebeck effect, magnetic tunneling junction, first-principles calculation

We calculated the Seebeck coefficients and the tunnel magneto-Seebeck (TMS) ratios of Fe(5ML)/MgO(5ML)/Fe(5ML) and Fe(5ML)/MgAl₂O₄(9ML)/Fe(5ML) magnetic tunneling junctions (MTJs) using the first-principles density functional method. The electronic transport coefficients of the MTJ were calculated from the Landauer formula. We obtained positive values of the Seebeck coefficients for the Fe/MgAl₂O₄/Fe MTJ around 300K, while we obtained negative ones for the Fe/MgO/Fe MTJ, which was explained by considering the energy dependence of the electronic conductance relative to the Fermi energy. For the Fe/MgO/Fe MTJ in parallel and anti-parallel configurations, large electronic conductance was obtained above the Fermi energy, which results in the negative Seebeck coefficients in almost all the temperatures, while for the Fe/MgAl₂O₄/Fe MTJ, large electronic conductance was obtained below the Fermi energy, which results in the positive ones. These results may help to understand the origin of the TMS effects.