Ultrafast magnetization dynamics of Nickel

Ultrafast electron and magnetization dynamics of Ni were studied by pump-probe reflection second harmonic generation with an experimental time resolution of approximate to 40 fs. No delay between initial electronic heating and demagnetization was observed within this time resolution. Thus, there is no need to introduce an independent spin temperature. Once the electron gas is thermalized, the recovery of magnetization obeys the classical magnetization curve. This was demonstrated for delay times up to 1 ns. The dependence of second harmonic yield on the azimuth of magnetization for selected pump-probe delays proved that the phase between even and odd contributions is zero.