Andreev Reflection Studies in GaMnAs/Nb Micro-Structures

ORAL

Abstract

The ability to measure the electron spin polarization of ferromagnetic materials at the interface with non-ferromagnetic materials is essential for spintronics applications. The spin polarization at ferromagnetic/non-ferromagnetic interfaces can be very different from the bulk spin polarization due to the surface states. Andreev spectroscopy has the ability of estimating the spin polarization for ferromagnetic materials. We use the Circular Transfer Line Method (CTLM) [1-2] to measure the Andreev reflection effect at GaMnAs/superconductor interface and to extract GaMnAs spin polarization. This technique works well for high-resistivity films and has other advantages over point contact and planar Andreev effect measurement geometries. We will present our recent results and contrast them with previous work, where we easily eliminate the bulk resistance contribution and the broadening of the superconducting gap. Furthermore, we found that a Schottky barrier is likely to form at the interface unless the interface is cleaned carefully and a high quality sample is used. This Schottky barrier can be confused as an actual Andreev effect.

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Authors

  • Hussein AbuJeib

    Miami Univ

  • John Royston

    Ball State University, Naval Research Laboratory, Washington, DC 20375, USA, Univ of Cincinnati, KITP China, U.C. Berkeley, FNAL, Cornell, West Virginia University, University of Pittsburgh, The Ohio State University, Carnegie Mellon University, Miami University, University of Notre Dame, University of Nebraska-Lincoln, Miami Univ, Australia National Univ., Miami Univ., Univ. of Cincinnati, Physics and Astronomy Department, Ohio University, Athens, OH 45701, Australian National University, University of Toledo, The University of Toledo, University of Toledo, Wright Center for Photovoltaics Innovation and Commercialization, University of Cincinnati, University of California, Davis

  • John Royston

    Ball State University, Naval Research Laboratory, Washington, DC 20375, USA, Univ of Cincinnati, KITP China, U.C. Berkeley, FNAL, Cornell, West Virginia University, University of Pittsburgh, The Ohio State University, Carnegie Mellon University, Miami University, University of Notre Dame, University of Nebraska-Lincoln, Miami Univ, Australia National Univ., Miami Univ., Univ. of Cincinnati, Physics and Astronomy Department, Ohio University, Athens, OH 45701, Australian National University, University of Toledo, The University of Toledo, University of Toledo, Wright Center for Photovoltaics Innovation and Commercialization, University of Cincinnati, University of California, Davis

  • John Royston

    Ball State University, Naval Research Laboratory, Washington, DC 20375, USA, Univ of Cincinnati, KITP China, U.C. Berkeley, FNAL, Cornell, West Virginia University, University of Pittsburgh, The Ohio State University, Carnegie Mellon University, Miami University, University of Notre Dame, University of Nebraska-Lincoln, Miami Univ, Australia National Univ., Miami Univ., Univ. of Cincinnati, Physics and Astronomy Department, Ohio University, Athens, OH 45701, Australian National University, University of Toledo, The University of Toledo, University of Toledo, Wright Center for Photovoltaics Innovation and Commercialization, University of Cincinnati, University of California, Davis

  • John Royston

    Ball State University, Naval Research Laboratory, Washington, DC 20375, USA, Univ of Cincinnati, KITP China, U.C. Berkeley, FNAL, Cornell, West Virginia University, University of Pittsburgh, The Ohio State University, Carnegie Mellon University, Miami University, University of Notre Dame, University of Nebraska-Lincoln, Miami Univ, Australia National Univ., Miami Univ., Univ. of Cincinnati, Physics and Astronomy Department, Ohio University, Athens, OH 45701, Australian National University, University of Toledo, The University of Toledo, University of Toledo, Wright Center for Photovoltaics Innovation and Commercialization, University of Cincinnati, University of California, Davis

  • John Royston

    Ball State University, Naval Research Laboratory, Washington, DC 20375, USA, Univ of Cincinnati, KITP China, U.C. Berkeley, FNAL, Cornell, West Virginia University, University of Pittsburgh, The Ohio State University, Carnegie Mellon University, Miami University, University of Notre Dame, University of Nebraska-Lincoln, Miami Univ, Australia National Univ., Miami Univ., Univ. of Cincinnati, Physics and Astronomy Department, Ohio University, Athens, OH 45701, Australian National University, University of Toledo, The University of Toledo, University of Toledo, Wright Center for Photovoltaics Innovation and Commercialization, University of Cincinnati, University of California, Davis