Element-specific spin and orbital momentum dynamics of Fe∕Gd multilayers

The role of orbital magnetism in the laser-induced demagnetization of Fe∕Gd multilayers was investigated using time-resolved x-ray magnetic circular dichroism at 2ps time resolution given by an x-ray streak camera. An ultrafast transfer of angular momentum from the spin via the orbital momentum to the lattice was observed which was characterized by rapidly thermalizing spin and orbital momenta. Strong interlayer exchange coupling between Fe and Gd led to a simultaneous demagnetization of both layers.