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

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. In conclusion, a theoretical framework is developed that can account for the signal amplitude, linewidth, and anisotropy.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [2] ;  [5]
  1. Stanford Univ., Stanford, CA (United States)
  2. Univ. of Iowa, Iowa City, IA (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States); The Univ. of Tokyo, Chiba (Japan)
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  5. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
OSTI Identifier:
1225766
Grant/Contract Number:
AC02-76SF00515
Type:
Published Article
Journal Name:
Physical Review. X
Additional Journal Information:
Journal Volume: 5; Journal Issue: 4; Journal ID: ISSN 2160-3308
Publisher:
American Physical Society
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; materials science; semiconductor physics; spintronics