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Ultrafast demagnetization of Pt magnetic moment in L1(0)-FePt probed by magnetic circular dichroism at a hard x-ray free electron laser

Publikace na Matematicko-fyzikální fakulta |
2019

Tento text není v aktuálním jazyce dostupný. Zobrazuje se verze "en".Abstrakt

Unraveling the origin of ultrafast demagnetization in multisublattice ferromagnetic materials requires femtosecond x-ray techniques to trace the magnetic moment dynamics on individual elements, but this could not yet be achieved in the hard x-ray regime. We demonstrate here the first ultrafast demagnetization dynamics in the ferromagnetic heavy 5d-transition metal Pt using circularly-polarized hard x-rays at an x-ray free electron laser (XFEL).

The decay time of laser-induced demagnetization of L1(0)-FePt is determined to be tau(Pt) = 0.61 +/- 0.04 ps using time-resolved x-ray magnetic circular dichroism at the Pt L-3 edge, whereas magneto-optical Kerr measurements indicate the decay time for the total magnetization as tau(total) < 0.1 ps. A transient magnetic state with a photomodulated ratio of the 3d and 5d magnetic moments is demonstrated for pump-probe delays larger than 1 ps.

We explain this distinct photo-modulated transient magnetic state by the induced-moment behavior of the Pt atom and the x-ray probing depth. Our findings pave the way for the future use of XFELs to disentangle atomic spin dynamics contributions.