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

摘要

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' = alpha J), where 0 < alpha < 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)Br-2, alpha = 0.20(5), C = 0.430(1) emu K/mol, 2J = -46(1)K, and 2J' = -9( 2) K and for Cu( pz) Cl-2, alpha = 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.