Femtosecond imaging of the spin dynamics of CoPt3 nanostructures

A powerful technique for imaging the spin dynamics of individual CoPt₃ submicron dots and thin CoPt₃ films with a temporal resolution of 150 fs and a spatial resolution of 300 nm by using femtosecond confocal magneto-optical microscopy is reported. The temporal variation of the differential polar Kerr signal of an individual CoPt₃ dot with a diameter of 1 mum at remanent state is obtained. The dynamics reflects the initial demagnetization during the pump excitation as well as the re-magnetization associated to the equilibrium between the spins and the lattice. The all optical switching of a CoPt₃ thin film using circularly polarized light is also reported.