Spin- and Symmetry-Filtering Combined Tunnel Magnetoresistance through Epitaxial MgO/EuS Tunnel Barriers

TL;DR

This study demonstrates high tunnel magnetoresistance in epitaxial FeCo/MgO/EuS junctions and investigates the impact of MgO thickness on conductance, revealing a rapid decline in magnetoresistance due to nonspecular conductance effects.

Contribution

It introduces a novel epitaxial magnetic tunnel junction with combined spin- and symmetry-filtering, and analyzes the effects of MgO thickness on magnetoresistance behavior.

Findings

Tunnel magnetoresistance reached 64% at 4.2 K.

Magnetoresistance drops rapidly for MgO thickness above 1 nm.

Nonspecular conductance affects the tunneling properties.

Abstract

We created epitaxial magnetic tunnel junctions of FeCo/MgO/EuS on MgO buffered Si (100). Tunnel magnetoresistance reached up to 64% at 4.2 K. An unexpected fast drop of magnetoresistance was recorded for MgO thickness above 1 nm, which is attributed to the forced nonspecular conductance across the EuS conduction band minimum located at the X point, rather than the desired Delta_1 conductance centered around the Gamma point.