STATIC PROPERTIES OF CSNIF3 - COMPARISON OF NUMERICAL RESULTS, EXPERIMENTAL-DATA, AND PREDICTIONS FROM SOLITON-BEARING MODELS

The numerical quantum transfer-matrix method has been applied to the s = 1 easy-plane ferromagnetic chain system CsNiF3. A detailed analysis of experimental data on the static properties reveals that the generally accepted spin Hamiltonian for this compound gives an accurate description of the individual chains for J/K(B) = 25 K and D/k(B) = 7.7 K. At temperatures up to several degrees Kelvin above the three-dimensional ordering temperature, deviations between theory and experiment are found that are attributed to the coupling between the chains. A comparison of the quantum-transfer-matrix-method results with various analytic results supports the description of solitary excitations in CsNiF3 by the classical sine-Gordon model, extended to include spin fluctuations out of the easy plane and quantum effects.