Using single quantum states as spin filters to study spin polarization in ferromagnets

TL;DR

This paper demonstrates how spin-resolved quantum states can serve as effective spin filters to measure spin-dependent tunneling in ferromagnets, revealing magnetic-field effects on electrochemical potentials.

Contribution

It introduces a novel method using single quantum states as spin filters to study spin polarization in ferromagnets, with experimental observations of magnetic-field-dependent shifts.

Findings

Spin-resolved quantum states act as spin filters for tunneling.

Magnetic-field-dependent shifts in electrochemical potential observed.

Shifts are smaller than expected from spin-polarized density of states.

Abstract

By measuring electron tunneling between a ferromagnet and individual energy levels in an aluminum quantum dot, we show how spin-resolved quantum states can be used as filters to determine spin-dependent tunneling rates. We also observe magnetic-field-dependent shifts in the magnet's electrochemical potential relative to the dot's energy levels. The shifts vary between samples and are generally smaller than expected from the magnet's spin-polarized density of states. We suggest that they are affected by field-dependent charge redistribution at the magnetic interface.