Spin-Polarized Electron Transport through Nanometer-Scale Al Grains

We had investigated the spin-polarized electron tunnelling through ensembles of nanometer scale Al grains embedded between two Co-reservoirs at 4.2K, and observed tunnelling-magnetoresistance (TMR) and the Hanle effect. The Spin-coherence time ($T$2 ), measured from the Hanle effect, is around nanoseconds. Fast dephasing is attributed to electron spin-precession in the local fringing fields. Dephasing does not destroy \textit{TMR}, in contrast to spin-relaxation. \textit{TMR }is strongly asymmetric with bias voltage, which we explain by spin-relaxation.