The effects of a magnetic barrier and a nonmagnetic spacer in tunnel structures

TL;DR

This paper theoretically investigates a novel magnetic tunnel junction with a magnetic barrier and nonmagnetic spacer, revealing oscillatory behavior in TMR and spin polarization influenced by quantum well states, useful for spin electronic device development.

Contribution

It introduces a new magnetic tunnel junction structure and analyzes its spin transport properties using transfer matrix and nearly-free-electron approximations.

Findings

TMR and spin polarization oscillate with spacer thickness and bias voltage.

Magnetic barrier enhances spin polarization and TMR.

Quantum well states cause oscillatory behavior.

Abstract

The spin-polarized transport is investigated in a new type of magnetic tunnel junction which consists of two ferromagnetic electrodes separated by a magnetic barrier and a nonmagnetic metallic spacer. Based on the transfer matrix method and the nearly-free-electron-approximation the dependence of the tunnel magnetoresistance (TMR) and electron-spin polarization on the nonmagnetic layer thickness and the applied bias voltage are studied theoretically. The TMR and spin polarization show an oscillatory behavior as a function of the spacer thickness and the bias voltage. The oscillations originate from the quantum well states in the spacer, while the existence of the magnetic barrier gives rise to a strong spin polarization and high values of the TMR. Our results may be useful for the development of spin electronic devices based on coherent transport.