HfO2 and SiO2 as barriers in magnetic tunneling junctions
HfO2 and SiO2 as barriers in magnetic tunneling junctions
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DOI：
10.1103/physrevb.95.184410
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发表时间：
2017-05
影响因子：
3.7
通讯作者：
Gokaran Shukla;T. Archer;S. Sanvito
中科院分区：
文献类型：
--
作者：
Gokaran Shukla;T. Archer;S. Sanvito
SiO2和HfO 2都是高k、宽禁带半导体，目前在微电子工业中用作栅极势垒。在这里，我们研究是否可以采用相同的材料，使磁性隧道结，这在原则上可以适用于集成在传统的硅技术。采用密度泛函理论和量子输运的非平衡绿色函数方法研究了Co[0001]/SiO_2 [001]/Co[0001]和Fe[001]/HfO_2 [001]/Fe[001]结的输运性质。在这两种情况下，我们发现了一个相当大的磁阻，这是通过分析的真实的带结构的磁铁和复杂的绝缘体。我们发现，由于高透射2′带在两个自旋方向上都穿过费米能级EF，因此Co基结不存在对称自旋过滤。然而，Co是强铁磁体的事实使得两个2′自旋子带的轨道贡献不同，产生磁阻。相比之下，对于Fe基结，对称性过滤对于费米能级和EF以下1 eV之间的能量窗口是有效的，其中1对称性有助于透射。
SiO2 and HfO2 are both high-k, wide-gap semiconductors, currently used in the microelectronic industry as gate barriers. Here we investigate whether the same materials can be employed to make magnetic tunnel junctions, which in principle can be amenable for integration in conventional Si technology. By using a combination of density functional theory and the nonequilibrium Green’s functions method for quantum transport we have studied the transport properties of Co[0001]/SiO2[001]/Co[0001] and Fe[001]/HfO2[001]/Fe[001] junctions. In both cases we found a quite large magnetoresistance, which is explained through the analysis of the real band structure of the magnets and the complex one of the insulator. We find that there is no symmetry spin filtering for the Co-based junction since the high transmission 2′ band crosses the Fermi level, EF, for both spin directions. However, the fact that Co is a strong ferromagnet makes the orbital contribution to the two 2′ spin subbands different, yielding magnetoresistance. In contrast for the Fe-based junction symmetry filtering is active for an energy window spanning between the Fermi level and 1 eV below EF, with 1 symmetry contributing to the transmission.