Bias voltage effects on tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) junctions: Comparative study with Fe/MgO/Fe(001) junctions
Bias voltage effects on tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) junctions: Comparative study with Fe/MgO/Fe(001) junctions
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DOI：
10.1103/physrevb.96.054428
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发表时间：
2017-08-21
影响因子：
3.7
通讯作者：
Miura, Yoshio
中科院分区：
文献类型：
--
作者：
Masuda, Keisuke;Miura, Yoshio
通过与Fe/MgO/Fe(001)磁性隧道结(MTJ)的比较，研究了偏压对MTJ自旋输运性质的影响。利用非平衡格林函数方法和密度泛函理论，计算了两种MTJ的偏置电压对磁阻(MR)比的影响。我们发现，在两种MTJ中，磁阻比都随着偏置电压的增加而减小，最终在一个临界偏置电压Vc时消失。我们还发现，MgAl2O4基MTJ的临界偏置电压Vc明显大于MgO基MTJ。由于Fe/MgAl2O4/Fe(001)超晶胞的面内晶格常数是Fe/MgO/Fe(001)超晶胞晶格常数的两倍，因此，MgAl2O4基MTJ中的Fe电极具有与通过折叠面内波矢布里渊区的MgO基MTJ中的Fe带结构相同的能带结构。结果表明，这种Fe能带结构的差异是镁铝酸镁和氧化镁MTJ临界偏置电压Vc差异的根源。
We investigate bias voltage effects on the spin-dependent transport properties of Fe/MgAl2O4/Fe(001) magnetic tunneling junctions (MTJs) by comparing them with those of Fe/MgO/Fe(001) MTJs. By means of the nonequilibrium Green's function method and the density functional theory, we calculate bias voltage dependencies of magnetoresistance (MR) ratios in both the MTJs. We find that in both the MTJs, the MR ratio decreases as the bias voltage increases and finally vanishes at a critical bias voltage Vc. We also find that the critical bias voltage Vc of the MgAl2O4-based MTJ is clearly larger than that of the MgO-based MTJ. Since the in-plane lattice constant of the Fe/MgAl2O4/Fe(001) supercell is twice that of the Fe/MgO/Fe(001) one, the Fe electrodes in the MgAl2O4-based MTJs have an identical band structure to that obtained by folding the Fe band structure of the MgO-based MTJs in the Brillouin zone of the in-plane wave vector. We show that such a difference in the Fe band structure is the origin of the difference in the critical bias voltage Vc between the MgAl2O4-and MgO-based MTJs.