Spin Fluctuations in Frustrated Kagomé Lattice System SrCr8Ga4O19 Studied by Muon Spin Relaxation

We have performed muon spin relaxation measurements of the frustrated kagomé lattice spin system SrCr8Ga4O19. Our results demonstrate the slowing down of the Cr spin fluctuations when cooling toward the susceptibility-cusp temperature Tg∼3.5 K. The saturation of the relaxation rate below Tg, together with its weak dependence on longitudinal field (LF) between 0 and 2 kG, indicates the presence of dynamic spin fluctuations persisting even at T∼100 mK without static order parameter. We propose a spin-liquid type ground state to explain an undecouplable Gaussian shape of the relaxation function observed at T≤Tg.