Impact of the interface quality of Pt/YIG(111) hybrids on their spin Hall magnetoresistance

TL;DR

This study investigates how the surface treatment of YIG substrates affects the spin Hall magnetoresistance in Pt/YIG hybrids, revealing that specific cleaning and annealing processes significantly enhance SMR performance.

Contribution

It demonstrates that surface treatments prior to Pt deposition critically influence the interface quality and the resulting spin Hall magnetoresistance in Pt/YIG hybrids.

Findings

Two-step surface treatment yields the highest SMR.

Carbon contamination reduces SMR in untreated samples.

Surface quality correlates with SMR magnitude.

Abstract

We study the influence of the interface quality of Pt/Y$_3$Fe$_5$O$_{12}$(111) hybrids on their spin Hall magnetoresistance. This is achieved by exposing Y$_3$Fe$_5$O$_{12}$(111) single crystal substrates to different well-defined surface treatments prior to the Pt deposition. The quality of the Y$_3$Fe$_5$O$_{12}$(YIG) surface, the Pt/YIG interface and the Pt layer is monitored \textit{in-situ} by reflection high-energy electron diffraction and Auger electron spectroscopy as well as \textit{ex-situ} by atomic force microscopy and x-ray diffraction. To identify the impact of the different surface treatments on the spin Hall magnetoresistance, angle-dependent magnetoresistance measurements are carried out at room temperature. The largest spin Hall magnetoresistance is found in Pt/YIG fabricated by a two-step surface treatment consisting of a "piranha" etch process followed by an annealing step at $500^\circ$C in pure oxygen atmosphere. Our data suggest that the small SMR in Pt/YIG without any surface treatments of the YIG substrate prior to Pt deposition is caused by a considerable carbon agglomeration at the Y$_3$Fe$_5$O$_{12}$ surface.