Role of domain nucleation and domain wall motion in all-optical helicity-dependent switching

Since the discovery of femtosecond laser pulse induced magnetization switching, all-optical helicity-dependent switching (AO-HDS) has emerged as a powerful technique in the manipulation of magnetization across various magnetic materials, notably without any applied magnetic field. Nevertheless, the underlying mechanisms of AO-HDS remain a subject of intensive debate. Here, we investigate the AO-HDS phenomenon through a complementary approach, employing anomalous Hall effect and microscope optical Kerr effect analyses on a 10 \ifmmode\times\else\texttimes\fi{} 10 \textmu{}m\texttwosuperior{} square Co/Pt multilayer with strong perpendicular magnetic anisotropy. Our focus is on the dynamics of magnetization switching induced by multiple picosecond circularly polarized laser pulses. We meticulously record the evolution of the anomalous Hall voltage as a function of time, revealing distinct ``jump'' and ``relaxation'' phases in the Hall signal. These phases are intricately linked to the processes of magnetic domain nucleation and domain wall propagation. Furthermore, we consider the influence of helicity-independent laser heating, domain pressure, and temperature gradients to understand the domain dynamics during the magnetization switching process. This comprehensive analysis not only sheds light on the role of micromagnetic evolution but also constitutes a pivotal step toward unraveling the complex mechanics of AO-HDS.