Magnetic Order In Quasi-Two-Dimensional Molecular Magnets Investigated With Muon-Spin Relaxation

We present the results of a muon-spin relaxation (mu+SR) investigation into magnetic ordering in several families of layered quasi-two-dimensional molecular antiferromagnets based on transition-metal ions such as S = 1/2 Cu2+ bridged with organic ligands such as pyrazine. In many of these materials magnetic ordering is difficult to detect with conventional magnetic probes. In contrast, mu+SR allows us to identify ordering temperatures and study the critical behavior close to T-N. Combining this with measurements of in-plane magnetic exchange J and predictions from quantum Monte Carlo simulations we may assess the degree of isolation of the 2D layers through estimates of the effective inter-layer exchange coupling and in-layer correlation lengths at T-N. We also identify the likely metal-ion moment sizes and muon stopping sites in these materials, based on probabilistic analysis of the magnetic structures and of muon-fluorine dipole-dipole coupling in fluorinated materials.