Effect of Quantum Tunneling on Spin Hall Magnetoresistance

TL;DR

This paper develops a comprehensive formalism that models how quantum tunneling and spin diffusion jointly influence spin Hall magnetoresistance in various bilayer systems, providing a unified approach to interpret experimental data.

Contribution

It introduces a formalism that simultaneously accounts for quantum tunneling and spin diffusion effects on spin Hall magnetoresistance in bilayer systems, unifying material parameters.

Findings

Quantifies the impact of material properties on magnetoresistance.

Provides a framework for interpreting quantum effects in experiments.

Suggests experimental methods to observe quantum features.

Abstract

We present a formalism that simultaneously incorporates the effect of quantum tunneling and spin diffusion on spin Hall magnetoresistance observed in normal metal/ferromagnetic insulator bilayers (such as Pt/YIG) and normal metal/ferromagnetic metal bilayers (such as Pt/Co), in which the angle of magnetization influences the magnetoresistance of the normal metal. In the normal metal side the spin diffusion is known to affect the landscape of the spin accumulation caused by spin Hall effect and subsequently the magnetoresistance, while on the ferromagnet side the quantum tunneling effect is detrimental to the interface spin current which also affects the spin accumulation. The influence of generic material properties such as spin diffusion length, layer thickness, interface coupling, and insulating gap can be quantified in a unified manner, and experiments that reveal the quantum feature of the magnetoresistance are suggested.