Frustrated magnetism of the spin-1 kagome antiferromagnet β-BaNi3(VO4)2(OH)2.

We propose the newly synthesized β-BaNi(VO)(OH)(space group: R-3m) as a candidate for the spin-1 kagome Heisenberg antiferromagnet (KHA). The compound features a uniform kagome lattice of Ni(S = 1) ions with a large interlayer distance. High-field measurements at low temperatures reveal a susceptibility local minimum at ∼ 9 T, resembling a 1/3 magnetization plateau as predicted by the pure S = 1 KHA model. Below ∼ 6 K, approximately 1% of the spins exhibit spin-glass order, which may be attributed to the nanocrystalline grain size of ∼ 50 nm. Despite the antiferromagnetic exchange coupling strength of ∼ 7 K, the majority of spins remain disordered down to ∼ 0.1 K as indicated by the observed power-law behaviors in magnetic specific heat C∝ T. Our results demonstrate that the low-energy magnetic excitations in β-BaNi(VO)(OH)are gapless, which contradicts the current theoretical expectations of the ideal model.