⁵¹V-NMR study of honeycomb lattice antiferromagnet InCu _2/3V_1/3O₃

We report here the results of ⁵¹V-NMR experiments as well as susceptibility and high-filed magnetization measurements on a spin-1/2 honeycomb lattice antiferromagnet InCu_2/3V_1/3O₃. The magnetization curve at 4.2 K showed no anomaly up to 54 T. A small anomaly around 38 K was found in the nuclear spin-latteice relaxation rate T ^-1₁ as well as the susceptibility, while NMR spectrum was temperature independent. Further, T^-1₁ showed a broad maximum around 15 K and a tendency to be constant towards the lowest temperature of 2 K. Our results suggest that a large spin fluctuation remains until 2 K without a specific magnetic long-range ordering. Preliminary NMR results for an oriented sample are also shown.