Study of individual ferromagnetic disks with femtosecond optical pulses

The magnetization dynamics of ferromagnetic disks made of CoPt3 and Ni80Fe20 has been investigated using a time resolved magneto-optical Kerr microscope. The spatial resolution of 500 nm combined to the pump and probe femtosecond laser pulses allows us to explore the magnetization dynamics of individual disks over a broad temporal regime ranging from 100 fs to 1 ns. In addition, our experimental configuration allows us to perform a dynamical imaging of the magnetization for a fixed delay between the pump and probe pulses. Such imaging has also been performed when the disk is initially switched to the reversed magnetization by the pump pulse.