Spin-Polarized Electron Transport through Nanometer-Scale Al Grains

TL;DR

This study explores spin-polarized electron tunneling through nanometer-scale aluminum grains between cobalt reservoirs at low temperature, revealing magnetoresistance effects, spin precession, and dephasing phenomena relevant for spintronic applications.

Contribution

It provides new insights into spin coherence and dephasing mechanisms in nanoscale aluminum grains, including measurements of $T_2^igstar$ and analysis of asymmetric TMR effects.

Findings

Measured spin-coherence time ~$ns$ using Hanle effect

Observed asymmetric TMR dependent on bias voltage

Attributed dephasing to local magnetic field-induced spin precession

Abstract

We investigate spin-polarized electron tunnelling through ensembles of nanometer scale Al grains embedded between two Co-reservoirs at 4.2K, and observe tunnelling-magnetoresistance (TMR) and effects from spin-precession in the perpendicular applied magnetic field (the Hanle effect). The spin-coherence time ($T_2^\star$) measured using the Hanle effect is of order $ns$. The dephasing is attributed to electron spin-precession in local magnetic fields. Dephasing process does not destroy $TMR$, which is strongly asymmetric with bias voltage. The asymmetric TMR is explained by spin relaxation in Al grains and asymmetric electron dwell times.