Laser-induced ultrafast magnetization dynamics in BiYIG/Co-based heterostructures: Complementary insights from pump-probe Faraday and Kerr rotation measurements
Phys. Rev. B 113, 094402 – Published 2 March, 2026
DOI: https://doi.org/10.1103/kcfj-t6f9
Abstract
Using pump-probe Faraday and Kerr rotation measurements, we investigate the ultrafast magnetization dynamics induced by femtosecond laser pulses in a BiYIG/Co-based heterostructure epitaxially grown on GGG(001) substrate. The Kerr measurements reveal the excitation of high-frequency exchange standing spin-wave modes, whereas the Faraday measurements detect only the ferromagnetic resonance mode. Moreover, the Kerr response exhibits faster remagnetization following the demagnetization dynamics. These differences are explained by considering the average magnetization profile of the magneto-optical (MO) Faraday effect and the unequal depth sensitivity of the MO Kerr effect. They also allow deeper insight into the mechanisms driving the magnetization dynamics. Furthermore, we identify in the Kerr signal a contribution induced by the strain pulse in the BiYIG layer and gadolinium gallium garnet (GGG) substrate, which is absent in the Faraday response and should not be misinterpreted as a magnetic effect. These findings establish important connections with existing literature on laser-induced ultrafast magnetization dynamics in magnetic garnets and advance the fundamental understanding of these dynamics.
