This new paper in Physical Review B shows that spin accumulation can produce unexpectedly large signals in ultrafast magneto-optical experiments, opening new ways to probe spin transport and dynamics.
Large spin accumulation signals in ultrafast magneto-optical experiments
Alberto Anadón, Harjinder Singh, Eva Díaz, Yann Le-Guen, Julius Hohlfeld, Richard B. Wilson, Gregory Malinowski, Michel Hehn and Jon Gorchon
Phys. Rev. B 112, 104437 – Published 25 September, 2025
DOI: 10.1103/5qnm-zgjt
Abstract:
Magneto-optical techniques have become essential tools in spintronics, enabling the investigation of spin dynamics in the ultrafast regime. A key challenge in this field has been to accurately isolate the contributions to magneto-optical signals of spin transport phenomena from the local magnetization dynamics. The contribution of transported and accumulated spins was long believed to be orders of magnitude smaller than that of the magnetization and thus previous approaches to disentangle these signals have relied on specific experimental designs, usually including thick metal layers. Here, we present experimental evidence demonstrating that the magneto-optical signal from ultrafast spin accumulations can, under certain conditions, be comparable to or even exceed that of the magnetic layer in a standard ultrafast demagnetization experiment. Our findings provide a framework for accessing and isolating these spin accumulations, allowing for time- and depth-dependent probing of transported spin and/or orbital angular momentum.
