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R. Abrudan, M. Hennecke, F. Radu, T. Kachel, K. Holldack, R. Mitzner, A. Donges, S. Khmelevskyi, A. Deák, L. Szunyogh, U. Nowak, S. Eisebitt, I. Radu:
"Element-Specific Magnetization Damping in Ferrimagnetic DyCo5 Alloys Revealed by Ultrafast X-ray Measurements";
Physica Status Solidi - Rapid Research Letters, 15 (2021), 2170029.

The dynamic response of magnetically ordered materials to an ultrashort external
stimulus depends on microscopic parameters, such as magnetic moment,
exchange, and spin-orbit interactions. Whereas it is well established that, in
multicomponent magnetic alloys and compounds, the speed of demagnetization
and spin switching processes has an element-specific character, the magnetization
damping was assumed to be a universal parameter for all constituent magnetic
elements irrespective of their different spin-orbit couplings and electronic struc-
ture. Herein, experimental and theoretical evidence for an element-specific mag-
netic damping parameter is provided by investigating the ultrafast magnetization
response of a high-anisotropy ferrimagnetic DyCo5 alloy to femtosecond laser
excitation. Strikingly different demagnetization and remagnetization dynamics of
Dy and Co magnetic moments is revealed by employing femtosecond laser pump-
X-ray magnetic circular dichroism probe measurements combined with atomistic
spin dynamics (ASD) simulations using ab initio calculated parameters. These
observations, fully corroborated by the ASD simulations, are linked to the element-
specific spin-orbit coupling strengths of Dy and Co, which are incorporated in the
phenomenological magnetization damping parameters. These findings can be
used as a recipe for tuning the speed and magnitude of laser-driven magnetic
processes and consequently allow control over various dynamic functionalities in
multicomponent magnetic materials.

http://dx.doi.org/10.1002/pssr.202170029