Polarized neutron scattering studies of the kagomé lattice antiferromagnet KFe3(OH)6(SO4)2

Abstract We report polarized neutron scattering studies of spin-wave excitations and spin fluctuations in the S = 5 2 kagom e ´ lattice antiferromagnet KFe 3 ( OH ) 6 ( SO 4 ) 2 (jarosite). Inelastic polarized neutron scattering measurements at 10 K on a single crystal sample reveal two spin gaps, associated with in-plane and out-of-plane excitations. The polarization analysis of quasi-elastic scattering at 67 K shows in-plane spin fluctuations with XY symmetry, consistent with the disappearance of the in-plane gap above the Neel temperature T N = 65 K . Our results suggest that jarosite is a promising candidate for studying the 2D XY universality class in magnetic systems.