Spin-Dependent Coulomb Blockade in Ferromagnet/Normal-Metal/Ferromagnet Double Tunnel Junctions

TL;DR

This paper theoretically investigates spin-dependent electron transport in ferromagnet/normal-metal/ferromagnet double tunnel junctions, revealing how cotunneling and Coulomb blockade influence magnetoresistance and spin accumulation.

Contribution

It introduces a detailed analysis of cotunneling effects and predicts a new anomalous region with oscillating tunnel magnetoresistance due to Coulomb blockade.

Findings

Coulomb blockade region is squeezed by cotunneling with antiparallel magnetizations.

A new anomalous region exhibits oscillating tunnel magnetoresistance.

Temperature affects both tunnel magnetoresistance and spin accumulation.

Abstract

We study theoretically the spin-dependent transport in ferromagnet/normal-metal/ferromagnet double tunnel junctions by special attention to cotunneling in the Coulomb blockade region. The spin accumulation caused by cotunneling squeezes the Coulomb blockade region when the magnetizations in the ferromagnetic electrodes are antiparallel. Outside the squeezed Coulomb blockade region, we propose a new anomalous region, where the sequential tunneling in one of the spin bands is suppressed by the Coulomb blockade and that in the other is not. In this region, the tunnel magnetoresistance oscillates as a function of bias voltage. The temperature dependences of the tunnel magnetoresistance and the magnitude of the spin accumulation are calculated.