SPIN DYNAMICS IN COPT3 ALLOY-FILMS - A MAGNETIC PHASE-TRANSITION IN THE FEMTOSECOND TIME-SCALE

We have measured the magnetization dynamics of an epitaxial CoPt3 allo y film using a magneto-optical pump-probe Kerr setup with 120 fs laser pulses. At high pump fluence, the film is driven from the ferro- to t he paramagnetic state with a characteristic time comparable to the pul se duration. The associated demagnetization occurs within the thermali zation time of the electrons to a Fermi distribution. These results de monstrate the feasibility of ultrafast magneto-optical devices. [S0163 -1829(98)00342-7].