Comment on Absence of detectable current-induced magneto-optical Kerr effects in Pt, Ta and W Appl. Phys. Lett. 109, 172402 (2016)

TL;DR

This paper defends previous measurements of spin polarization in W and Pt films via the magneto-optic Kerr effect, countering claims that results were due to heating artifacts and asserting the detectability of SHE polarization.

Contribution

It provides a rebuttal to critiques by clarifying the validity of previous SHE polarization measurements using MOKE techniques.

Findings

Original MOKE measurements are accurate and not artifacts.

SHE polarization in W and Pt can be detected with proper MOKE methods.

Critiques attributing signals to heating effects are addressed and refuted.

Abstract

We recently reported measurements of spin polarization in W and Pt thin films produced by the spin Hall effect (SHE) using a magneto-optic Kerr effect (MOKE) system based on crossed polarizers that detects changes in light intensity. Riego et al used a generalized magneto-optical ellipsometry system that in principle can distinguish pure optical reflectivity from magneto-optic signals, but were unable to detect SHE polarization in their nominally W, Ta and Pt films. They argued that our results are spurious and likely due to resistive heating which temporally modulates the film temperature and reflectivity, and that any SHE polarization is too small to be detected in metal films. In this comment, we argue that our original results are correct as presented, and discuss why