Band-folding-driven high tunnel magnetoresistance ratios in (111)-oriented junctions with SrTiO3 barriers
Band-folding-driven high tunnel magnetoresistance ratios in (111)-oriented junctions with SrTiO3 barriers
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DOI：
10.1103/physrevb.106.134438
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发表时间：
2022-10-31
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;Itoh, Hiroyoshi;Miura, Yoshio
本文从理论上研究了（111）取向SrTiO_3势垒磁性隧道结（MTJ）、Co/SrTiO_3/Co（111）和Ni/SrTiO_3/Ni（111）的隧道磁电阻（TMR）效应。结合第一性原理计算和Landauer公式的分析表明，Co基MTJ具有超过500%的高TMR比，而Ni基MTJ具有较小的值（290%）。由于SrTiO 3的面内晶格周期性约为fcc Co（Ni）的原始晶胞的两倍，因此Co（Ni）的原始能带在对应于MTJ超晶胞的ab平面的k（x）-k（y）平面中折叠。我们发现这种能带折叠在Co（Ni）的λ（1）态中给出了一种半金属能带结构，这种半金属λ（1）态的相干隧穿产生了高的TMR比。我们还揭示了Co和Ni基MTJ之间TMR比的差异可以通过费米能级下λ（1）带中不同的s轨道权重来理解。
We theoretically study the tunnel magnetoresistance (TMR) effect in (111)-oriented magnetic tunnel junctions (MTJs) with SrTiO3 barriers, Co/SrTiO3/Co(111) and Ni/SrTiO3/Ni(111). Our analysis combining the first-principles calculation and the Landauer formula shows that the Co-based MTJ has a high TMR ratio over 500%, while the Ni-based MTJ has a smaller value (290%). Since the in-plane lattice periodicity of SrTiO3 is about twice that of the primitive cell of fcc Co (Ni), the original bands of Co (Ni) are folded in the k(x)-k(y) plane corresponding to the ab plane of the MTJ supercell. We find that this band folding gives a half-metallic band structure in the Lambda(1) state of Co (Ni) and the coherent tunneling of such a half-metallic Lambda(1) state yields a high TMR ratio. We also reveal that the difference in the TMR ratio between the Co- and Ni-based MTJs can be understood by different s-orbital weights in the Lambda(1) band at the Fermi level.