Interface states in CoFe$_{2}$O$_{4}$ spin-filter tunnel junctions

ORAL

Abstract

Spin-filter tunneling is a promising way to generate highly spin-polarized current, a key component for spintronics applications. In this work we explore the tunneling conductance across the spin-filter material CoFe$_{2}$O$_{4}$ interfaced with Au electrodes, a geometry which provides nearly perfect lattice matching at the CoFe$_{2}$O$_{4}$/Au(001) interface.\footnote{P. Lukashev, et al., Phys. Rev. B, \textbf{88}, 134430 (2013).} Using density functional theory calculations we demonstrate that interface states play a decisive role in controlling the transport spin polarization in this tunnel junction. For a realistic CoFe$_{2}$O$_{4}$ barrier thickness, we predict a tunneling spin polarization of about $-$60{\%}. We show that this value is lower than what is expected based solely on considerations of the spin-polarized band structure of CoFe$_{2}$O$_{4}$, and therefore that these interface states can play a detrimental role. We argue that this is a rather general feature of ferrimagnetic ferrites and could make an important impact on spin-filter tunneling applications.

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Authors

  • Pavel Lukashev

    • Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA

  • J.D. Burton

    • University of Nebraska-Lincoln
    • Univ of Nebraska - Lincoln
    • University of Nebraska - Lincoln
    • Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA

  • Alexander Smogunov

    • CEA, Institut Rayonnement Mati\`ere de Saclay, SPCSI, F-91191 Gif-sur-Yvette Cedex, France

  • Julian Velev

    • Department of Physics, Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00931, USA
    • Department of Physics, Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, PR 00931-3344, USA

  • E.Y. Tsymbal

    • University of Nebraska-Lincoln
    • Univ of Nebraska - Lincoln
    • University of Nebraska - Lincoln
    • Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
    • Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, United States