APS/J.-Y. Bigot

Figure 1: A physicist, previously unable to distinguish between the charge and the spin of electrons, now probes the magnetization dynamics of a ferromagnetic nickel-iron grating with femtosecond pulses of $66eV$ light, after illuminating the grating with a lower energy $1.6eV$ pulse of light. Both pulses are polarized in the plane of incidence (the plane defined by the incoming and outgoing rays of light). (Inset) By varying the delay between the pump and the probe, it is possible to map out the characteristic time ($τth$) in which the film demagnetizes.