NMR Evidence for Field-induced Magnetic Ordering at 30 T in the Haldane Compound PbNi₂V₂O₈

Abstract

⁵¹V-NMR measurements of the Haldane compound PbNi₂V₂O₈ at 30 T have been performed by using a hybrid magnet installed at National Institute for Materials Science. The NMR spectrum begins to split at 12 K with decreasing temperature. The temperature at which the NMR spectrum begins to split well agrees with the temperature at which the magnetization takes the minimum. The splitting of the NMR spectrum gives microscopic evidence for the presence of the field-induced antiferromagnetic ordering. The splitting has grown uniformly with decreasing temperature, suggesting that the transition is of second order and the magnitude of the ordered moment is uniform. The upper limit of the magnitude of the ordered moment was estimated from dipole field calculations.