Magneto-optical Kerr spectra of gold induced by spin accumulation

TL;DR

This study measures the magneto-optical Kerr effect in gold induced by spin accumulation from adjacent cobalt layers, revealing gold's potential as a highly sensitive optical magnetometer for spintronic applications.

Contribution

It demonstrates the first measurement of Kerr rotation in gold caused by spin accumulation, highlighting gold's exceptional sensitivity to spin magnetic moments.

Findings

Kerr rotation per A/m exceeds 1 urad near interband transition threshold.

Gold's optical response to spin moments is more sensitive than ferromagnetic metals.

Gold can serve as an ultra-sensitive optical magnetometer for spin detection.

Abstract

We report the magneto optic Kerr effect (MOKE) angle of Au magnetically excited by spin accumulation. We perform time resolved polar MOKE measurements on Au/Co heterostructures. In our experiment, the ultrafast optical excitation of the Co drives spin accumulation into an adjacent Au layer. The spin accumulation, together with spin-orbit coupling, leads to non-zero terms in the off-diagonal conductivity tensor of Au, which we measure by recording the polarization and ellipticity of light reflected from the Au surface for photon energies between 1.3 and 3.1 eV. At energies near the interband transition threshold of Au, the Kerr rotation per A/m exceeds 1 urad. Typical values for Kerr rotation per moment in transition ferromagnetic metals like Ni are < 10 nrad per A/m, while predicted values for heavy metals like Pt or W are < 13 nrad per A/m. The exceptional sensitivity of the optical properties of Au to spin magnetic moments make Au to be an exceptionally sensitive optical magnetometer, with potential applications in the development of optospintronic technologies.