Results of magnetization and high-field ESR studies of the new spin-1 Haldane-chain material [Ni(C2H8N2)2NO2](BF4) (NENB) are reported. A definite signature of the Haldane state in NENB was obtained. From the analysis of the frequency-field dependence of magnetic excitations in NENB, the spin-Hamiltonian parameters were calculated, yielding Delta = 17.4 K, g_parallel = 2.14, D = 7.5 K, and |E| = 0.7 K for the Haldane gap, g factor and the crystal-field anisotropy constants, respectively. The presence of fractional S = 1/2 chain-end states, revealed by ESR and magnetization measurements, is found to be responsible for spin-glass freezing effects. In addition, extra states in the excitation spectrum of NENB have been observed in the vicinity of the Haldane gap, which origin is discussed.
@article{arxiv.0709.1779,
title = {Magnetic properties of the Haldane-gap material NENB},
author = {E. Cizmar and M. Ozerov and O. Ignatchik and T. P. Papageorgiou and J. Wosnitza and S. A. Zvyagin and J. Krzystek and Z. Zhou and C. P. Landee and B. R. Landry and M. M. Turnbull and J. L. Wikaira},
journal= {arXiv preprint arXiv:0709.1779},
year = {2015}
}