Interdiffusion-controlled Kondo suppression of injection efficiency in metallic nonlocal spin valves

L. O'Brien, D. Spivak, J. S. Jeong, K. A. Mkhoyan, P. A. Crowell, C. Leighton

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Nonlocal spin valves (NLSVs) generate pure spin currents, providing unique insight into spin injection and relaxation at the nanoscale. Recently it was shown that the puzzling low temperature nonmonotonicity of the spin accumulation in all-metal NLSVs occurs due to a manifestation of the Kondo effect arising from dilute local-moment-forming impurities in the nonmagnetic material. Here it is demonstrated that precise control over interdiffusion in Fe/Cu NLSVs via thermal annealing can induce dramatic increases in this Kondo suppression of injection efficiency, observation of injector/detector separation-dependent Kondo effects in both charge and spin channels simultaneously, and, in the limit of large interdiffusion, complete breakdown of standard Valet-Fert-based models. The Kondo effect in the charge channel enables extraction of the exact interdiffusion profile, quantifying the influence of local moment density on the injection efficiency and presenting a well-posed challenge to theory.

Original languageEnglish (US)
Article number014413
JournalPhysical Review B
Issue number1
StatePublished - Jan 11 2016

Bibliographical note

Funding Information:
University of Minnesota UM National Science Foundation NSF DMR-0819885 DMR 1420013 DMR-1507048 European Research Council ERC 299376 This work was funded by Seagate Technology Inc., the University of Minnesota (UMN) National Science Foundation (NSF) Materials Research Science and Engineering Center (MRSEC) under Awards No. DMR-0819885 and No. DMR 1420013, as well as NSF DMR-1507048. L.O''B. acknowledges a Marie Curie International Outgoing Fellowship under the European Research Council (ERC) 7th framework programme (Project No. 299376). Parts of this work were carried out in the UMN Characterization Facility and Minnesota Nano Center, which receives partial support from the NSF MRSEC and NSF NNIN programs, respectively. We thank David Deen of Seagate for productive conversations.

Publisher Copyright:
© 2016 American Physical Society.

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