Exchange splitting and bias-dependent transport in EuO spin filter tunnel barriers

¹  Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology - Cambridge, MA 02139, USA
²  Institute of Solid State Research, Research Centre Jülich - 52428 Jülich, Germany, EU

Corresponding author: mart.mueller@fz-juelich.de

Received: 27 July 2009
Accepted: 3 November 2009

Abstract

We report on transport measurements in EuO-based tunnel junctions, studying the characteristic features of spin filter tunneling in magnetic insulators. Current-voltage (I-V) curves show a unique voltage dependence that reveals the interplay between direct and spin-selective Fowler-Nordheim (FN) tunneling. Successive onsets of FN tunneling give direct evidence for a spin filtering effect, without relying on the use of external magnetic fields for spin detection. The variation of the effective tunnel barrier height below the Curie temperature was extracted from temperature-dependent I-V characteristics, and systematically correlates with the spontaneous magnetization of EuO. The magnitude of the exchange splitting was deduced and allows the evaluation of spin filter efficiency of EuO spin filter tunnel barriers by fully electrical means.