Muon-spin-rotation measurements in thekagomélattice systems: Cr-jarosite and Fe-jarosite

We have examined the magnetic properties of the frustrated kagomé lattice spin systems ${\mathrm{KFe}}_3$(OH${)}_6$(${\mathrm{SO}}_4$ ${)}_2$ (Fe-jarosite) and ${\mathrm{KCr}}_3$(OH${)}_6$(${\mathrm{SO}}_4$ ${)}_2$ (Cr-jarosite) using the μSR technique. In Fe-jarosite, a clear muon precession signal in zero field was found below 55 K, corresponding to the long-range order of Fe moments. In Cr-jarosite spin fluctuations persist without clear signature of spin freezing even at T = 25 mK, far below ${\mathit{T}}_{\mathit{g}}$∼2 K where the history dependence in the magnetic susceptibility appears. © 1996 The American Physical Society.