Evidence for Exchange-Coupled Linear Chains in Cu(NH3)4SO4·H2O

Abstract

Published values of specific heat and magnetic susceptibility for Cu${\left(\mathrm{N}{\mathrm{H}}_3\right)}_4$S${\mathrm{O}}_4$·${\mathrm{H}}_2$O show broad maxima at a temperature roughly ten times the Néel temperature. It is shown that the behavior of these quantities above the Néel temperature may be explained qualitatively, and also quantitatively at temperatures near the maxima, in terms of an isotropic, antiferromagnetic exchange interaction between neighboring spins in linear chains of copper ions. The exchange energy, $\frac{\mathrm{}\left|J\right|\mathrm{}}{k}$, is equal to 3.15±0.2°K.