Low-T dynamics in the highly frustrated S=32 kagomé bilayers: A phenomenological function for a spin liquid state?

A μSR study of the spin dynamics of the archetypes of the highly frustrated magnets, SrCr 9p Ga 12-9p O 19 and Ba 2 Sn 2 ZnGa 10-7p Cr 7p O 22 , is summarized. Especially, low dilutions of the magnetic network could be achieved and we take advantage of the close similarity between these kagome bilayers to single out their typical properties. The phenomenological model for the μ + relaxation, based on sporadic dynamics due to spin excitations in a singlet sea, proposed by Uemura et al., is extended to all fields, temperature and defects range. Its connection to a RVB picture is discussed.