The new material Li9Fe3(P2O7)3(PO4)2 is a rare example of a classical Heisenberg kagomé antiferromagnet that we have investigated using Nuclear Magnetic Resonance and magnetization measurements down to low temperatures. Our measurements reveal a characteristic magnetization plateau at 1/3 of the saturation magnetization below T ∼ 5 K. While this was predicted a long time ago, a clear experimental proof was still missing due to the scarcity of suitable compounds: because of their large antiferromagnetic interaction J ∼ 600 K, they all require unattainable applied magnetic fields in order to reach this 1=3 plateau! Furthermore, our 31P NMR measurements indicates the development of anisotropic short-range correlations concomitantly with a gapless spin-lattice relaxation time T1 ∼ kBT=ℏS, which may point to the presence of a semiclassical nematic spin-liquid state, also predicted for the Heisenberg kagome antiferromagnetic model.
Ref: E. Kermarrec , R. Kumar, G. Bernard, R. Hénaff, P. Mendels, F. Bert, P. L. Paulose, B. K. Hazra, and B. Koteswararao
Phys. Rev. Lett. 127, 157202 (2021)