Magnetic specific heat of linear chains with Heisenberg exchange and crystal-field anisotropy forS=1

Abstract

Estimates of the specific heat $C$ are presented for the infinite one-dimensional array of spins $S=1\mathrm{}$ with isotropic nearest-neighbor coupling $J$ and an axial zero-field splitting $\Delta$. The results are obtained from extrapolation of $C$ for finite chains. For a number of ratio's $\frac{\Delta }{J}$ (including all sign combinations of $J$ and $\Delta$) curves are presented for all temperatures except for the region near $T=0\mathrm{}$. Attention is given to the justification of the extrapolation formula. In the case of ferromagnetic exchange a second maximum may appear in $C$ for small $\Delta$. Its position and amplitude are strongly dependent on $\frac{\Delta }{J}$. For antiferromagnetic coupling, $C$ is only slightly dependent on the sign and magnitude of $\Delta$ for small $\Delta$.