Texture-dependent all-optical switching in ferromagnetic films via stochastic nucleation of nanoscale domains

Controlling magnetic textures at ever smaller length scales and timescales is of fundamental and technological interest. External stimuli capable of acting at the nanoscale pose a challenge, motivating alternative approaches that exploit the intrinsic inhomogeneity of magnetic textures. Here we use a Pt/Co/Pt ferromagnetic thin film to investigate magnetization reversal with circularly polarized picosecond laser pulses. Magnetic force microscopy reveals stochastic nucleation of complex nanotextured domains from an initial monodomain state. Subsequent illumination of these domains with laser pulses induces deterministic and homogeneous magnetization switching. We find that the domain growth depends on the complexity of the texture, revealing a helicity- and texture-dependent mechanism that contrasts with temperature-gradient-driven domain expansion. We complement our observations with a stochastic model in which domain nucleation is governed by light helicity and the local magnetic environment. These results provide an insight into the mechanism of multipulse helicity-dependent all-optical switching.