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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.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Tunnel magnetoresistance, Magnetic tunnel junction, Spintronics

Date published: 2022-10-31

Publisher: American Physical Society (APS)

Journal:

• Physical Review B (ISSN: 1550235X) vol. 106 issue. 13 134438

Funding:

• Japan Society for the Promotion of Science JP22H04966
• Japan Society for the Promotion of Science JP20H02190
• Japan Society for the Promotion of Science JP21H01750
• Japan Society for the Promotion of Science JP20K14782
• Japan Science and Technology Agency JPMJCR21C1

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1103/physrevb.106.134438

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Updated at: 2024-04-11 13:28:22 +0900

Published on MDR: 2024-04-11 12:30:24 +0900