Single-crystal magnetic-susceptibility measurements on the nearly two-dimensional Heisenberg system [${\left(\mathrm{N}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\right)}_2$N${\mathrm{H}}_2$] [Cu${\mathrm{Cl}}_4$]Cl

The magnetic susceptibilities of both polycrystalline and single-crystal samples of the compound diethylenetriammonium chlorocuprate (II), [${\left(\mathrm{N}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\right)}_2$N${\mathrm{H}}_2$] [Cu${\mathrm{Cl}}_4$]Cl, have been measured from 1.6 to 160 °K. The compound undergoes a phase transition to an antiferromagnetic state at 11.8 °K with the $c$ crystallographic axis as the preferred axis. Above the transition, the magnetic properties of this material reflect its two-dimensional structural characteristics, with the predominate feature being a ferromagnetic alignment of spins within a network of isolated copper ions. The high-temperature polycrystalline data have been fitted to a variety of models for a quadratic lattice. When the data are fit to the two-dimensional Heisenberg model for the quadratic lattice, a value of $\frac{J}{k}=18.7\mathrm{}$ °K results. Although an excellent fit is achieved over a wide temperature range, the data are not able to discriminate between models in which there are variable degrees of anisotropy in the exchange. Finally, a comparison is made between [${\left(\mathrm{N}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_2\right)}_2$N${\mathrm{H}}_2$] [Cu${\mathrm{Cl}}_4$]Cl and the thoroughly studied ${\left[{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{N}{\mathrm{H}}_3\right]}_2$Cu${\mathrm{Cl}}_4$.