We report single-pulse all-optical helicity-independent toggle switching in CoHo and CoDy alloy thin films, demonstrating a magnetization reversal mechanism distinct from previously observed ultrafast or precessional pathways. Unlike the subpicosecond switching in Gd-based ferrimagnets, we show that reversal occurs on a microsecond timescale via domain wall motion and coalescence processes. This dynamic is initiated by complete demagnetization of the Co sublattice following ultrafast laser excitation, with angular momentum transfer from the rare-earth element (Ho or Dy) leading to deterministic toggle behavior. Using both time-resolved magneto-optical Kerr effect measurements and Hall bar electrical detection, we establish that the reversal process is inherently slow and governed by domain dynamics. Complementary micromagnetic simulations support a model in which slight asymmetries induced by a spin current during the recovery from a demagnetized state guide the system toward a reversed saturated final magnetization. These results extend the class of materials that can exhibit deterministic magnetization reversal without magnetic fields or helicity, offering promising new routes for optically driven spintronic applications.

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• Micromagnetism
• Spin dynamics
• Spintronics
• Ultrafast magnetic effects