Probing current-induced magnetic fields in Au|YIG heterostructure with low-energy muon spectroscopy

TL;DR

This study uses low-energy muon spectroscopy to map the depth-dependent magnetic fields in Au|YIG heterostructures, revealing how interface roughness influences current-induced magnetic fields relevant to spin-Hall effect research.

Contribution

It demonstrates the application of LE-muSR to probe buried magnetic interfaces and models the impact of interface roughness on local magnetic fields.

Findings

Maximum Oersted field shift of 0.4 G at Au surface

Suppressed magnetic shift near Au|YIG interface due to dipolar fields

Interface roughness explains the observed magnetic field variations

Abstract

We investigated the depth dependence of current-induced magnetic fields in a bilayer of a normal metal (Au) and a ferrimagnetic insulator (Yttrium Iron Garnet - YIG) by using low energy muon spectroscopy (LE-muSR). This allows us to explore how these fields vary from the Au surface down to the buried Au|YIG interface, which is relevant to study physics like the spin-Hall effect. We observed a maximum shift of 0.4 G in the internal field of muons at the surface of Au film which is in close agreement to the value expected for Oersted fields. As muons are implanted closer to the Au|YIG interface the shift is strongly suppressed, which we attribute to the dipolar fields present at the Au|YIG interface. Combining our measurements with modelling, we show that dipolar fields caused by the finite roughness of the Au|YIG interface consistently explains our observations. Our results, therefore, gauge the limits on the spatial resolution and the sensitivity of LE-muSR to the roughness of the buried magnetic interfaces, a prerequisite for future studies addressing current induced fields caused by the spin-Hall effect.