Spin flip scattering in magnetic junctions

TL;DR

This paper investigates various mechanisms affecting spin-dependent tunneling in magnetic junctions, including impurities, magnons, and Coulomb blockade, revealing their distinct impacts on resistance and magnetoresistance at different conditions.

Contribution

It provides a comprehensive analysis of spin flip scattering processes and their quantitative effects on magnetoresistance in magnetic junctions, highlighting new contributions from impurities, magnons, and Coulomb effects.

Findings

Impurities increase resistance and reduce magnetoresistance, saturating at low temperatures.

Magnon-assisted tunneling causes a $T^{3/2}$ decrease in magnetoresistance and a $V^{3/2}$ non-ohmic resistance.

Surface antiferromagnetic magnons lead to $T^2$ and $V^2$ contributions to magnetoresistance and resistance.

Abstract

Processes which flip the spin of an electron tunneling in a junction made up of magnetic electrodes are studied. It is found that: i) Magnetic impurities give a contribution which increases the resistance and lowers the magnetoresistance, which saturates at low temperatures. The conductance increases at high fields. ii) Magnon assisted tunneling reduces the magnetoresistance as $T^{3/2}$, and leads to a non ohmic contribution to the resistance which goes as $V^{3/2}$, iii) Surface antiferromagnetic magnons, which may appear if the interface has different magnetic properties from the bulk, gives rise to $T^2$ and $V^2$ contributions to the magnetoresistance and resistance, respectively, and, iv) Coulomb blockade effects may enhance the magnetoresistance, when transport is dominated by cotunneling processes.