Spin order in the Heisenberg kagome antiferromagnet MgF e3(OH)6 C l2

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)6Cl2. The compound has been synthesized by selectively replacing the magnetic ions in the triangular planes of its parent compound of deformed pyrochlore Fe2(OH)3Cl with nonmagnetic Mg. Whereas Fe2(OH)3Cl showed antiferromagnetic order below TN=8.5K with persistent spin fluctuations, MgFe3(OH)6Cl2 showed an antiferromagnetic transition at an enhanced TN value of 9.9 K. Susceptibility, high-field magnetization, and neutron-diffraction studies suggest that MgFe3(OH)6Cl2 is a Heisenberg-like spin system with a 120° nearest-neighbor spin structure confined in the kagome plane and spin-vector chirality of q=-1 below TN. Muon spin-rotation/-relaxation studies demonstrate that the persisting spin fluctuations are suppressed relative to Fe2(OH)3Cl. 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.