Ultrafast magnetization dynamics of Nickel

Ultrafast electron and magnetization dynamics of Ni were studied by pump-pr obe reflection second harmonic generation with an experimental time resolut ion of approximate to 40 fs. No delay between initial electronic heating an d 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 magnetiz ation curve. This was demonstrated for delay times up to 1 ns. The dependen ce of second harmonic yield on the azimuth of magnetization for selected pu mp-probe delays proved that the phase between even and odd contributions is zero.