Classical Spin Liquid State In The S=5/2 Heisenberg Kagome Antiferromagnet Li9fe3 (P2o7)(3)(Po4)(2)

We investigate the low temperature magnetic properties of a S = 5/2 Heisenberg kagome antiferromagnet, the layered monodiphosphate Li9Fe3(P2O7)(3)(PO4)(2), using magnetization measurements and P-31 nuclear magnetic resonance. An antiferromagnetic-type order sets in at T-N = 1.3 K and a characteristic magnetization plateau is observed at 1/3 of the saturation magnetization below T* similar to 5 K. A moderate P-31 NMR line broadening reveals the development of anisotropic short-range correlations concomitantly with a gapless spin-lattice relaxation time T-1 similar to k(B)T/(h) over barS, which may point to the presence of a semiclassical nematic spin-liquid state predicted for the Heisenberg kagome antiferromagnetic model or to the persistence of the zero-energy modes of the kagome lattice under large magnetic fields.