  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.
