title: muSR study of the quantum dynamics in the frustrated S=3/2 kagomé bilayers.
abstract: We present muSR experiments in the S=3/2 kagomé bilayer compound Ba(2)Sn(2)ZnGa(10-7p)Cr(7p)O22 [BSZCGO(p)] and compare it to the isostructural SrCr(9p)Ga(12-9p)O19 [SCGO(p)], including for the latter new results for p > or =0.89. Quantum-dynamical low energy magnetic excitations are evidenced in this novel compound. We study the evolution of the muon relaxation rate with p, T, and field. A phenomenological model for the muon relaxation based on sporadic dynamics due to spin excitations in a singlet sea proposed by Uemura et al. is extended to all fields and T range. Its connection to the RVB picture is discussed, and we argue that such coherent states might mediate the interactions between "impurities" which induce the spin glass freezing.
authors.affiliation: Laboratoire de Physique des Solides, UMR 8502, Université Paris-Sud, 91405 Orsay, France.
authors.forename: D
authors.initials: D
authors.lastname: Bono
authors.forename: P
authors.initials: P
authors.lastname: Mendels
authors.forename: G
authors.initials: G
authors.lastname: Collin
authors.forename: N
authors.initials: N
authors.lastname: Blanchard
authors.forename: F
authors.initials: F
authors.lastname: Bert
authors.forename: A
authors.initials: A
authors.lastname: Amato
authors.forename: C
authors.initials: C
authors.lastname: Baines
authors.forename: A D
authors.initials: AD
authors.lastname: Hillier