Static properties of quantum spin S=1 chains: TMNB, TMNC and CsNiF₃

Abstract

The zero-field parallel and perpendicular susceptibility and the zero-field specific heat of the quantum easy-plane S=1 Heisenberg spin chains are calculated numerically and applied to TMNB, TMNC and CsNiF3. New values of the model parameters are estimated from fitting procedures. As to CsNiF3, the in-plane specific heat, the field-dependent magnetization and the spin-wave dispersion are also evaluated for a given choice of the microscopic parameters (J/kB=20.5 K, A/J=0.425) and compared with measured quantities. An overall agreement with experiment is revealed.

Direct Simulations of the Quantum Model for CsNiF3

“…we computed the zero-field specific heat for sizes up to N = 9; 2. we modified the boundary conditions; 3. we adapted a new extrapolation procedure, locating first the position and height of the peaks in the zero-field specific heat and then the parts of the curves around the maxima. Our new data for the specific heat (extracted from system sizes N < 9) are presented in Table I, according to the choice of parameters displayed in the first row and taken after [1,2,4]. Within quoted error bars we do not find deviations with respect to our earlier results (Fig.…”

“…Due to the lack of exact descriptions and to some discrepancies, numerical simulations of the corresponding spin models have been performed both for statics and dynamics ( [1,2] First, we briefly recall our previous results [1]. Extending the length of the chains (N < 8), we calculated the zero-field specific heat C, the parallel susceptibility xii and the perpendicular susceptibility xi, and we fitted them to the available zero-field experimental data.…”

Large-Scale Simulations of Phase Transitions and Low-Dimensional Magnets

“…and Kamieniarz (1992a). The variation of the molar finite-size specific heat (Campana, Caramico D'Auria, Esposito, Esposito and Kamieniarz, 1996) with respect to 1/N is plotted for temperatures entire temperature range the 1/N dependence shows linear behaviour so that the extrapolated data can be extracted with the accuracy of an order of 0.1% and within this error they agree with the transfer matrix data plotted versus 1/m 2 in the same figure.…”

“…14 for sets (57), (56), (55), respectively and the results of measurements (Dupas and Renard, 1977) are depicted by full circles. For set (57) found in (Campana et al, 1992a), the agreement is excellent whereas some deviations of the order of 5-6% occur (Fig. 15) near the maximum if set (56) is used.…”

“…The microscopic parameters of the Hamiltonian describing CsNiF 3 were first determined (Steiner, Villain and Windsor, 1976) by fitting the observed energy spectra to the theoretical magnon (55) dispersion relation. Due to the discrepances between the theoretical predictions and the observed static properties evidenced in numerical calculations, new fitting procedures were carried out by Delica, de Jonge, Kopinga, Leschke and Mikeska (1991) and Campana et al (1992a) which led to the following sets of the parameters 83 and (56) (57) respectively. In both numerical procedures the values of g were fixed and only J and A were subject to variation.…”