Parity Effect and Tunnel Magnetoresistance of Ferromagnet / Superconductor / Ferromagnet Single-Electron Tunneling Transistors

TL;DR

This paper theoretically investigates the tunnel magnetoresistance (TMR) in ferromagnet/superconductor/ferromagnet single-electron transistors, highlighting the parity effect and how TMR varies with island size and spin relaxation.

Contribution

It introduces a theoretical analysis of TMR considering the parity effect in ferromagnet/superconductor/ferromagnet transistors, emphasizing the role of excess electrons and island size.

Findings

TMR exists even without spin accumulation in the plateau region.

TMR increases as the superconducting island size decreases.

Spin relaxation rate can be estimated from TMR measurements.

Abstract

We theoretically study the tunnel magnetoresistance(TMR) of ferromagnet / superconductor / ferromagnet single-electron tunneling transistors with a special attention to the parity effect. It is shown that in the plateau region, there is no spin accumulation in the island even at finite bias voltage. However, the information of the injected spin is carried by the excess electron and thus the TMR exists. The spin relaxation rate of the excess electron can be estimated from the TMR. We also show that the TMR increases with decreasing the size of the superconducting island.