Spin dynamics in a structurally ordered non-Fermi liquid compound:   YbRh_2Si_2
  Muon spin relaxation (muSR) experiments have been carried out at low temperatures in the non-Fermi-liquid heavy-fermion compound YbRh_2Si_2. The longitudinal-field muSR relaxation function is exponential, indicative that the dynamic spin fluctuations are homogeneous. The relaxation rate 1/T_1 varies with applied field as H^{-y}, y = 1.0 \pm 0.1, which implies a scaling law of the form \chi''(\omega) \propto \omega^{-y} f(\omega/T), \lim_{x\to0} f(x) = x for the dynamic spin susceptibility. 
K. Ishida, D. E. MacLaughlin, O. O. Bernal, R. H. Heffner, G. J.   Nieuwenhuys, O. Trovarelli, C. Geibel, and F. Steglich