Time evolution of domain-wall motion induced by nanosecond laser pulses

The time evolution of the magnetization normal component change in a garnet film with a labyrinthine domain structure under the action of circularly and linearly polarized laser pump pulses (the pulse duration is 5 ns; the wavelength is 527 nm) has been studied. The dynamic state of the magnetic film was registered using an induction method with a time resolution of 1 ns. It was found that for the initial state of the magnetic film with an equilibrium domain structure, the form of the photomagnetization pulse reflects the time evolution of a domain-wall motion. The domain-wall motion initiated by the circularly polarized laser pump pulse continues in the same direction for a time more than an order of magnitude exceeding the laser pulse duration. In general, the time evolution of the domain-wall movement occurs in three stages. The separation of the contributions to the photomagnetization from the polarization-dependent and polarization-independent effects was carried out. The photomagnetization pulses that reflect the contributions by the aforementioned effects differ by form, and more than two orders of magnitude by duration. Their form doesn't change under a magnetic bias field change, only the photomagnetization pulse amplitude does: for the polarization-dependent contribution, it's an even function of the field, and for the polarization-independent contribution, it's an odd function. The interconnection between the polarization-dependent and polarization-independent effects, on the one hand, and the domain-wall displacement and the change of the film's saturation magnetization, on the other hand, was identified and described.