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

We study the influence of the interface quality of Pt/Y₃Fe₅O₁₂(111) hybrids on their spin Hall magnetoresistance. This is achieved by exposing Y₃Fe₅O₁₂(111) single crystal substrates to different well-defined surface treatments prior to the Pt deposition. The quality of the Y₃Fe₅O₁₂(YIG) surface, the Pt/YIG interface and the Pt layer is monitored in-situ by reflection high-energy electron diffraction and Auger electron spectroscopy as well as 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 °C in pure oxygen atmosphere. Our data suggest that the small spin Hall magnetoresistance in Pt/YIG without any surface treatments of the YIG substrate prior to Pt deposition is caused by a considerable carbon agglomeration at the Y₃Fe₅O₁₂ surface.