Magnetic susceptibility of quasi-one-dimensional Ising superantiferromagnets FeTAC and MCl2 · 2NC5H5 (M = Co, Fe): Approximation with L × ∞ and L × L × ∞ chain clusters

The temperature dependence of the zero-field susceptibilities of 2D and 3D Ising lattices with anisotropic coupling is analyzed. Infinite 2D and 3D lattices are approximated, respectively, by ensembles of independent L × ∞ and L × L × ∞ chain clusters that are infinitely long in the strong-coupling (J) direction. This approach is used as a basis for a quantitative description of available experimental data on the magnetic susceptibilities of the 2D anisotropic Ising ferromagnet [(CH₃)₃NH]FeCl₃ · 2H₂O (FeTAC) and the quasi-one-dimensional 3D systems CoCl₂ · 2NC₅H₅ and FeCl₂ · 2NC₅H₅ in the entire experimental temperature range. A method is proposed for determining the relative interchain coupling strength J'/J from the maximum susceptibility value, which improves the accuracy of estimates for J'/J by more than an order of magnitude.