Statistical characterization of the spin Hall magnetoresistance in YIG/Pt heterostructures

TL;DR

This study statistically analyzes the spatial variation of spin Hall magnetoresistance (SMR) in YIG/Pt heterostructures, revealing Gaussian distribution within samples and significant variation between samples, linked to interface quality differences.

Contribution

It provides the first detailed statistical characterization of SMR variations across and between YIG/Pt heterostructures, highlighting the importance of interface quality.

Findings

SMR follows a Gaussian distribution within samples.

Inter-sample SMR variation can reach ~30%.

Interface quality variations likely cause SMR amplitude differences.

Abstract

The spin Hall magnetoresistance (SMR) is widely used to study the interplay between charge and spin currents in bilayers of a magnetic insulator and a normal metal. However, not much is known about the spatial variation of the SMR across the surface of one and the same sample. In this work, we investigate the statistical distribution of the SMR in hundreds of nominally identical Hall bar structures patterned into prototypical yttrium iron garnet (YIG)/Pt heterostructures. We find a Gaussian-distributed SMR with a narrow standard deviation of approximately 10$\,$% of the mean value in each YIG/Pt bilayer studied. However, the variation of the mean SMR between different YIG/Pt samples can be as large as ~30$\,$%, despite nominally identical fabrication conditions. This demonstrates that spatial variations of the SMR amplitude must not be neglected, in particular when comparing different heterostructures. On a microscopic level, local variations of the interface quality captured by the spin mixing conductance are the most likely origin for the observed SMR amplitude variations.