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Séminaire « Physique du spin & magnétisme » de l’INSP

Soft x-rays, a local probe for the understanding of ultrafast demagnetization - Emmanuelle Jal - Mardi 14 mars 2017 à 11 h

INSP - 4 place Jussieu - 75252 PARIS Cedex 05 - Barre 22-32 - 4e étage, salle 407

Emmanuelle Jal - LCPMR

Abstract

The discovery of laser induced ultrafast magnetization dynamics by Beaurepaire et al. has stimulated an intense research activity and opened up a new field in condensed matter physics. Even after two decades of studies and debates, the mechanisms of ultrafast demagnetization remain disputed. In order to bring new experimental information into this field, and with the advent of femtosecond X-rays sources, we decided to use time resolved soft X-rays based pump/probe techniques. Indeed, contrary to IR and visible radiation, X-rays can be easily turned into an element-specific and local probe of the magnetization. First I will show results obtained by time-resolved small angle x-ray scattering on granular FePt. Then I will present results obtained by time-resolved x-ray resonant magnetic reflectivity on Ni thin films. In conclusion I will give some outlooks on questions that soft x-ray could help to solve in this field.