title: Low-energy spin dynamics of the s = 1/2 kagome system herbertsmithite.
abstract: The low-energy (ε = ħω < 1 meV), low-temperature (T = 0.05 K) spin dynamics of the s = 1/2 kagome candidate herbertsmithite are probed in the presence of magnetic fields up to 2.5 T. The zero-field spectra reveal a very weak continuum of scattering at T = 10 K and a broad inelastic peak centred at ε(max) = 0.2 meV at lower temperatures, T < 1 K. The broad peak is found to be strongly damped, with a liquid-like structure factor implying correlations at length scales up to r = 6 Å. The field dependence of the peak appears to follow the Zeeman splitting of s = 1/2 excitations, consistent with the weakly split 'doublets' observed in low-temperature specific heat. A possible explanation of these observations is a short-range correlated state involving defect spins between the kagome planes and moments in the kagome layers.
authors: Institut Laue-Langevin, 6 rue Jules Horowitz, F-38042 Grenoble, France. nilsen@ill.fr
authors: G J
authors: GJ
authors: Nilsen
authors: M A
authors: MA
authors: de Vries
authors: J R
authors: JR
authors: Stewart
authors: A
authors: A
authors: Harrison
authors: H M
authors: HM
authors: Rønnow