Interface states in CoFe2O4 spin-filter tunnel junctions

Authors

Pavel V. Lukashev, University of Nebraska-LincolnFollow
John D. Burton, University of Nebraska-LincolnFollow
Alexander Smogunov, CEA, Institut Rayonnement Matiere de Saclay, France
Julian P. Velev, University of Puerto Rico-San JuanFollow
Evgeny Y. Tsymbal, University of Nebraska-LincolnFollow

Date of this Version

10-31-2013

Citation

PHYSICAL REVIEW B 88, 134430 (2013).DOI: 10.1103/PhysRevB.88.134430

Comments

Copyright (c) 2013 American Physical Society. Used by permission.

Abstract

Spin-filter tunneling is a promising way to generate highly spin-polarized current, a key component for spintronics applications. In this paper we explore the tunneling conductance across the spin-filter material CoFe₂O₄ interfaced with Au electrodes, a geometry which provides nearly perfect lattice matching at the CoFe₂O₄/Au(001) interface. 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 CoFe₂O₄ 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 CoFe₂O₄, 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