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Center for Nonlinear Studies |
The direct manipulation of spins via light may provide a path toward ultrafast energy-efficient devices. However, distinguishing the microscopic processes that can occur during ultrafast laser excitation in magnetic alloys is challenging. I present a computational framework to simulate the out-of-equilibrium conditions arising in ultrafast laser experiments, and how transient response functions may be extracted to facilitate comparison to experimental observables relating to magnetism and topological band features. Further, the method is applied to study laser-induced magnetization dynamics in the Heusler compound Co2MnGa, a ferro-magnetic half-metal. By combining theory and experiment, we disentangle the competition between three ultrafast light-induced processes that occur in Co2MnGa: same-site Co-Co spin transfer, intersite Co-Mn spin transfer, and ultrafast spin flips mediated by spin-orbit coupling. By measuring and simulating the dynamic magnetic asymmetry across the entire M-edges of the two magnetic sublattices involved, we uncover the relative dominance of these processes at different probe energy regions and times during the laser pulse. Our combined approach enables a comprehensive microscopic interpretation of laser-induced magnetization dynamics on time scales shorter than 100 femtoseconds.
Host: Anders Niklasson