Helicity-dependent all-optical domain wall motion in ferromagnetic thin films

Abstract

Domain wall displacement in Co/Pt thin films induced by not only femtosecond but also picosecond laser pulses is demonstrated using time-resolved magneto-optical Faraday imaging. We evidence multipulse helicity-dependent laser-induced domain wall motion in all-optical switchable Co/Pt multilayers with a laser energy below the switching threshold. Domain wall displacement of $\ensuremath{\sim}2$ nm per 2-ps pulse is achieved. By investigating separately the effect of linear and circular polarization, we reveal that laser-induced domain wall motion results from a complex interplay between pinning, temperature gradient, and helicity effect. Then, we explore the microscopic origin of the helicity effect acting on the domain wall. These experimental results enhance the understanding of the mechanism of all-optical switching in ultrathin ferromagnetic films.