We have studied the ultrafast magneto-optical response of
CoPt3 ferromagnetic nanodots with diameters ranging from 0.2 to 1 μm. Our experiments combine an accurate temporal resolution using
femtosecond laser pulses and a high spatial resolution (\(\leqslant\)300 nm)
obtained with a reflective confocal Kerr microscope. Our experimental
approach allows exploring the dynamics of the magnetization of magnetic
nanostructures over a broad temporal scale ranging from 100 fs to 1 ns. We
report the corresponding relaxation behavior of the electrons and the spins
initially excited with a large excess energy above the Fermi level.
78.20.Ls Magnetooptical effects 78.47+p Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter 42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics
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