LAUSR

Abstract The generation of ultrashort hot-electron pulses in metallic heterostructures offers attractive perspectives for the ultrafast spin manipulation on the picosecond time scale. In such approach, the hot-electron pulses are produced by exciting a non-magnetic capping layer with femtosecond infrared laser pulses. These hot-electron pulses propagate towards a buried magnetic layer to trigger ultrafast demagnetization. Lately, it was shown that the demagnetization onset and characteristic demagnetization times are both affected by the transport regime (ballistic or diffusive) of the photo-excited hot-electrons. In this work, we show that the hot-electron pulses produced by photo-exciting a Al(3)/Ta(3)/Cu(60) capping layer undergo a temporal stretching and delays when they go across a [Co(0.1)/Ni(0.6)]x5 multilayer. These information were extracted from a study of hot-electron induced demagnetization in CoDy alloys by means of Time-Resolved X-Ray Magnetic Circular Dichroism.