Origin of the magnetoresistance in oxide tunnel junctions determined through electric polarization control of the interface

Hisashi Inoue, Adrian G. Swartz, Nicholas J. Harmon, Takashi Tachikawa, Yasuyuki Hikita, Michael E. Flatté, Harold Y. Hwang

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)

Abstract

The observed magnetoresistance (MR) in three-terminal (3T) ferromagnet-nonmagnet (FM-NM) tunnel junctions has historically been assigned to ensemble dephasing (Hanle effect) of a spin accumulation, thus offering a powerful approach for characterizing the spin lifetime of candidate materials for spintronics applications. However, due to crucial discrepancies of the extracted spin parameters with known materials properties, this interpretation has come under intense scrutiny. By employing epitaxial artificial dipoles as the tunnel barrier in oxide heterostructures, the band alignments between the FM and NM channels can be controllably engineered, providing an experimental platform for testing the predictions of the various spin accumulation models. Using this approach, we have been able to definitively rule out spin accumulation as the origin of the 3T MR. Instead, we assign the origin of the magnetoresistance to spin-dependent hopping through defect states in the barrier, a fundamental phenomenon seen across diverse systems. A theoretical framework is developed that can account for the signal amplitude, linewidth, and anisotropy.

Original languageEnglish
Article number041023
JournalPhysical Review X
Volume5
Issue number4
DOIs
Publication statusPublished - 2015
Externally publishedYes

Keywords

  • Materials Science
  • Semiconductor Physics
  • Spintronics

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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