Observation of Coherent Helimagnons and Gilbert damping in an Itinerant   Magnet
  We study the magnetic excitations of itinerant helimagnets by applying time-resolved optical spectroscopy to Fe0.8Co0.2Si. Optically excited oscillations of the magnetization in the helical state are found to disperse to lower frequency as the applied magnetic field is increased; the fingerprint of collective modes unique to helimagnets, known as helimagnons. The use of time-resolved spectroscopy allows us to address the fundamental magnetic relaxation processes by directly measuring the Gilbert damping, revealing the versatility of spin dynamics in chiral magnets. (*These authors contributed equally to this work) 
J. D. Koralek, D. Meier, J. P. Hinton, A. Bauer, S. A. Parameswaran,   A. Vishwanath, R. Ramesh, R. W. Schoenlein, C. Pfleid...
cond-mat.str-el cond-mat.mtrl-sci