Tunnel magnetoresistance in double spin filter junctions

TL;DR

This paper theoretically investigates a novel double spin filter magnetic tunnel junction, demonstrating that it can achieve extremely high tunnel magnetoresistance and spin polarization, which are promising for future spintronic devices.

Contribution

The study introduces a new double spin filter junction structure and analyzes its TMR and spin polarization dependence on various parameters, showing potential for enhanced spintronic applications.

Findings

TMR can reach up to 99% in the double SF junction.

Spin polarization exceeds that of single SF junctions with optimal NM layer thickness.

TMR and polarization depend strongly on NM layer thickness, bias, and temperature.

Abstract

We consider a new type of magnetic tunnel junction, which consists of two ferromagnetic tunnel barriers acting as spin filters (SFs), separated by a nonmagnetic metal (NM) layer. Using the transfer matrix method and the free-electron approximation, the dependence of the tunnel magnetoresistance (TMR) on the thickness of the central NM layer, bias voltage and temperature in the double SF junction are studied theoretically. It is shown that the TMR and electron-spin polarization in this structure can reach very large values under suitable conditions. The highest value of the TMR can reach 99%. By an appropriate choice of the thickness of the central NM layer, the degree of spin polarization in this structure will be higher than that of the single SF junctions. These results may be useful in designing future spin-polarized tunnelling devices.