We report 51V-NMR study on a high-quality powder sample of volborthite Cu3V2O7(OH)2/2H2O, a spin-1/2 Heisenberg antiferromagnet on a distorted kagome lattice formed by isosceles triangles. In the magnetic fields below 4.5 T, a sharp peak in the nuclear spin-lattice relaxation rate 1/T1 accompanied with line broadening revealed a magnetic transition near 1 K. The low temperature phase shows anomalies such as a Lorentzian line shape, a 1/T1 propto T behavior indicating dense low energy excitations, and a large spin-echo decay rate 1/T2 pointing to unusually slow fluctuations. Another magnetic phase appears above 4.5 T with less anomalous spectral shape and dynamics.
@article{arxiv.0906.2846,
title = {Phase Diagram and Spin Dynamics in Volborthite with a Distorted Kagome Lattice},
author = {M. Yoshida and M. Takigawa and H. Yoshida and Y. Okamoto and Z. Hiroi},
journal= {arXiv preprint arXiv:0906.2846},
year = {2017}
}