Muon-spin-rotation measurements in the<i>kagomé</i>lattice systems: Cr-jarosite and Fe-jarosite

Abstract

We have examined the magnetic properties of the frustrated kagom\'e 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 \ensuremath{\mu}SR 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 ${\mathit{T}}_{\mathit{g}}$\ensuremath{\sim}2 K where the history dependence in the magnetic susceptibility appears. \textcopyright{} 1996 The American Physical Society.