Spin order in the Heisenberg kagome antiferromagnet MgFe3(OH)6Cl2

Spin behaviors on kagome lattices have received increased attention because of their exotic magnetic states. Here, we report magnetic ordering in the S = 2 kagome antiferromagnet MgFe3(OH)(6)Cl-2. The compound has been synthesized by selectively replacing the magnetic ions in the triangular planes of its parent compound of deformed pyrochlore Fe-2(OH)(3)Cl with nonmagnetic Mg. Whereas Fe-2(OH)(3)Cl showed antiferromagnetic order below T-N = 8.5 K with persistent spin fluctuations, MgFe3(OH)(6)Cl-2 showed an antiferromagnetic transition at an enhanced T-N value of 9.9 K. Susceptibility, high-field magnetization, and neutron-diffraction studies suggest that MgFe3(OH)(6)Cl-2 is a Heisenberg-like spin system with a 120 degrees nearest-neighbor spin structure confined in the kagome plane and spin-vector chirality of q = -1 below T-N. Muon spin-rotation/-relaxation studies demonstrate that the persisting spin fluctuations are suppressed relative to Fe-2(OH)(3)Cl. The present paper reports the experimental realization of an S = 2 kagome antiferromagnet, highlighting a real system with a quasiclassical Heisenberg spin, which may also be a valuable reference system for quantum Heisenberg kagome antiferromagnets.