Magnetic And Thermodynamic Properties Of Ni(C10h8n2)(2)Ni(Cn)(4)Center Dot H2o: A S=1 Heisenberg Antiferromagnetic Chain With Strong In-Plane Anisotropy And Subcritical Exchange Coupling

The results of experimental studies of the magnetic and thermodynamic quantities and ESR data of a magnetic chain compound Ni(C10H8N2)(2)Ni(CN)(4).H2O are reported. The system is identified as an S = 1 planar Heisenberg antiferromagnetic chain with subcritical exchange coupling and strong in-plane anisotropy. The influence of in-plane anisotropy is discussed with respect to the validity of a theoretical model proposed for S = 1 Heisenberg chains with strong planar anisotropy. The analysis suggests that in-plane anisotropy should be considered in any attempt to find a compound potentially located at the boundary between the Haldane and large-D phases.