Two-dimensional spin-1/2 rectangular Heisenberg antiferromagnets: Simulation and experiment

We have simulated and analyzed the susceptibility of a series of two-dimensional (2D) spin-1/2 rectangular Heisenberg antiferromagnetic (as well as mixed exchange antiferromagnetic/ferromagnetic) lattices as a function of J, J' and temperature, where J is the dominant magnetic exchange interaction and J', the orthogonal interaction, is related to J by J' = alpha J, where a can vary from 0 to 1. Previous studies of the compounds pyrazineformatocopper(II) nitrate [Cu(pz)(HCO2)](NO3), catena-2-aminopyrimidinedichlorocopper(II) [Cu(2-apm)Cl-2], and catena-pyrazinediazidocopper(II) [Cu(pz)(N-3)(2)] indicated that these systems had 2D magnetic spin-spin interactions. However, there were no 2D models that could capture the behavior of any measurable bulk properties of the compounds. The previous authors fit the susceptibility data of the respective compounds to a 1D antiferromagnetic chain with a mean-field correction, or did not fit the data at all. We use the simulations to create this fit function in order to test the 2D model proposed for these spin systems.