[8a-A413-1~7] 10.3 Spin devices, magnetic memories and storages

▼ [8a-A413-2] Theory for bias voltage effects on spin-dependent transport properties in Fe/MgAl₂O₄/Fe(001) junctions

〇Keisuke Masuda¹, Yoshio Miura^1,2 (1.NIMS, 2.KIT)

Keywords:magnetic tunneling junctions, bias voltage effects

In this work, we theoretically study bias voltage effects on tunneling magnetoresistive properties in Fe/MgAl₂O₄/Fe(001) magnetic tunneling junctions (MTJs) by comparing them with those in typical Fe/MgO/Fe(001) MTJs. We calculated bias voltage dependences of magnetoresistance (MR) ratios in both the MTJs by using the density-functional theory and the nonequilibrium Green’ function method. We see that in both the MTJs, the MR ratio decreases as the bias voltage V increases and eventually vanishes at a critical value V_c. We also see that the MgAl₂O₄-based MTJ has a larger V_c than the MgO-based one. Since the in-plane lattice constant of Fe/MgAl₂O₄/Fe(001) is twice as that of Fe/MgO/Fe(001), the Fe electrodes in the MgAl₂O₄-based MTJ have an identical band structure to that obtained by folding the Fe band structure of the MgO-based MTJs. From detailed analyses of band-resolved transmittances, we clarified that the difference in V_c between the MgAl₂O₄- and MgO-based MTJs is attributed to such a band-folding effect.