Spin-accumulation induced magneto-optical Kerr spectra of Au
Year: 2021
Type: preprint
Abstract: We report the real and imaginary magneto optic Kerr angle of Au with spin accumulation. To measure the MOKE spectra of Au, we perform time-resolved polar Magneto optic Kerr effect (TR-MOKE) measurements on Au/Co heterostructures. Ultrafast optical excitation of the Co drives spin accumulation into an adjacent 210nm thick Au layer. The spin accumulation, together with spin-orbit coupling, leads to non-zero terms in the off-diagonal conductivity tensor of Au. To measure these off-diagonal terms, we record the polarization and ellipticity of light reflected from the Au surface for photon energies between 1.3 and 3.1 eV. We also perform density functional theory calculations of the optical conductivity tensor of Au in the presence of spin-accumulation. Our theoretical and experimental values for MOKE spectra of Au agree. We find Au to be an exceptionally sensitive optical magnetometer. At energies near the interband transition threshold of Au, the Kerr rotation per A/m exceeds 1 {\mu}rad. Typical values for Kerr rotation per moment in transition ferromagnetic metals like Ni are < 10 nrad / A/m. The exceptional sensitivity of the optical properties of Au to spin magnetic moments is due to strong spin-orbit coupling in d-states of Au, and the fact that spin accumulation leads to a magnetic moment localized to s-states near the Fermi-level.
Source: arXiv (Cornell University)
Authors: V. Ortiz, Sinisa Coh, Richard B. Wilson
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3203218800