Magnetic susceptibility of quasi-one-dimensional Ising superantiferromagnets FeTAC and MCl_2*2NC_5H_5 (M=Co, Fe): Approximations with L x oo and L x L x oo 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 x oo and L x L x oo 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 magnet [(CH_3)_3NH]FeCl_32H_2O (FeTAC) and the quasi-one-dimensional 3D magnets CoCl_22NC_5H_5 and FeCl_2*2NC_5H_5 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 magnetude.