Spin dependent photoelectron tunnelling from GaAs into magnetic Cobalt

TL;DR

This study demonstrates spin-dependent photoelectron tunneling from GaAs into magnetic Cobalt, showing measurable spin asymmetry influenced by light helicity and bias voltage, with potential implications for spintronic devices.

Contribution

It provides experimental evidence of spin-dependent tunneling from GaAs into magnetic Cobalt, highlighting the effects of bias and surface recombination on spin asymmetry.

Findings

Spin asymmetry reaches +/- 6% around zero bias.

Asymmetry decreases to +/- 2% at -1.6 V bias.

Sign of asymmetry correlates with Cobalt magnetization direction.

Abstract

The spin dependence of the photoelectron tunnel current from free standing GaAs films into out-of- plane magnetized Cobalt films is demonstrated. The measured spin asymmetry (A) resulting from a change in light helicity, reaches +/- 6% around zero applied tunnel bias and drops to +/- 2% at a bias of -1.6 V applied to the GaAs. This decrease is a result of the drop in the photoelectron spin polarization that results from a reduction in the GaAs surface recombination velocity. The sign of A changes with that of the Cobalt magnetization direction. In contrast, on a (nonmagnetic) Gold film A ~ 0%.