Interface states in CoFe2O4 spin-filter tunnel junctions

TL;DR

This study investigates how interface states affect spin-polarized tunneling in CoFe2O4-based spin filters, revealing that interface states can significantly reduce spin polarization and impact spintronics device performance.

Contribution

The paper demonstrates through density functional theory that interface states critically influence spin polarization in CoFe2O4 spin-filter tunnel junctions, highlighting their detrimental effect.

Findings

Interface states lower the tunneling spin polarization to about -60%.

Interface states can diminish spin polarization beyond predictions from bulk band structure.

The results suggest a general impact of interface states in ferrimagnetic ferrite spin filters.

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 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 this is a rather general feature of ferrimagnetic ferrites and could make an important impact on spin-filter tunneling applications.