Demagnetization following optical excitation in nickel and permalloy films

Time-resolved pump–probe second-harmonic (SH) response following optical excitation has been studied in nickel and permalloy films. Experimental data indicate that the odd SH field represents the transient magnetization, i.e. the behavior of the spin subsystem, while the electron subsystem generates the even SH field. Delays between odd and even SH fields of about 200 fs and 650 fs were detected for nickel and permalloy films, respectively. We found that the dynamics of the odd SH field is influenced by the polarization of the pump pulse. This dependence on excitation conditions suggests a difference in surface and bulk magnetization dynamics. Received: 25 November 2001 / Revised version: 27 March 2002 / Published online: 11 June 2002