Rectangular two-dimensional antiferromagnetic systems: Analysis of copper(II) pyrazine dibromide and dichloride

The structure of copper pyrazine dibromide (or dichloride) consists of dihalide-bridged copper chains parallel to the c-axis with the copper sites linked in a perpendicular direction by bridging pyrazine molecules parallel to the b-axis. Superexchange interactions are propagated through both halides and pyrazine so the magnetic structure is a rectangular layer with two exchange strengths, J and J′ (J′ = αJ), where 0 < α < 1. The susceptibility of a rectangular antiferromagnetic Heisenberg lattice with S = 1/2 has been simulated using Quantum Monte Carlo techniques and the results compared to the experimental data. Best fits of the magnetic susceptibility data to the simulated data yield: for Cu(pz)Br2, α = 0.20(5), C = 0.430(1) emu K/mol, 2J = −46(1) K, and 2J′ = −9(2) K and for Cu(pz)Cl2, α = 0.30(5), C = 0.426(1) emu K/mol, 2J = −28(1) K, and 2J′ = −8(2)) K. The values are in good agreement with the literature and thus demonstrate the effectiveness of the technique for rectangular lattices.

The susceptibilities of the rectangular antiferromagnetic Heisenberg lattices Cu(pyrazine)Cl2 and Cu(pyrazine)Br2 with S = 1/2 have been simulated using Quantum Monte Carlo techniques and the results compared to the experimental data.Figure optionsDownload as PowerPoint slide