Band-folding-driven high tunnel magnetoresistance ratios in (111)-oriented junctions with <math>
  <msub>
    <mi>SrTiO</mi>
    <mn>3</mn>
  </msub>
</math> barriers

Keisuke Masuda; Hiroyoshi Itoh; Yoshiaki Sonobe; Hiroaki Sukegawa; Seiji Mitani; Yoshio Miura

doi:10.1103/physrevb.106.134438

論文 Band-folding-driven high tunnel magnetoresistance ratios in (111)-oriented junctions with

{SrTiO}_{3}

barriers

Keisuke Masuda (National Institute for Materials Science) ; Hiroyoshi Itoh ; Yoshiaki Sonobe ; Hiroaki Sukegawa (National Institute for Materials Science) ; Seiji Mitani (National Institute for Materials Science) ; Yoshio Miura (National Institute for Materials Science)

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Keisuke Masuda, Hiroyoshi Itoh, Yoshiaki Sonobe, Hiroaki Sukegawa, Seiji Mitani, Yoshio Miura. Band-folding-driven high tunnel magnetoresistance ratios in (111)-oriented junctions with

{SrTiO}_{3}

barriers. Physical Review B. 2022, 106 (13), 134438. https://doi.org/10.1103/physrevb.106.134438

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(abstract)

We theoretically study the tunnel magnetoresistance (TMR) effect in novel (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 as that of the primitive cell of fcc Co (Ni), the original bands of Co (Ni) are folded in the kx-ky plane corresponding to the ab-plane of the MTJ supercell. We find that this band folding gives a half-metallic band structure in the Lambda1 state of Co (Ni) and the coherent tunneling of such a half-metallic Lambda1 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 Lambda1 band at the Fermi level.

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