ESR study in X, Q and W-band of ferromagnetic copper(II) layer compounds involving bridging dicarboxylate anions

A series of layered hydroxide-based copper(II) compounds, involving adipate, trans-hexenedioate or muconate anion as bridging unit, is investigated by ESR spectroscopy. Intense signals observed in X, Q, and W-bands are related to rather strong in-plane ferromagnetic exchange coupling (5.5–18.1 K) between copper(II) ions. These signals shift substantially when approaching 3D ordering temperature, due to the increasing dipolar magnetic field created by the strongly correlated spins. The g-tensorʹs values in W-band point to a two sublattice structure of elongated octahedra with nearly perpendicular long axes. The structure is discussed on the basis of the related cobalt(II) and copper(II) hydroxy-terephthalates. The latter, Cu2(OH)2(tp), shows a FMR signal close to Tc=4.5 K, in good agreement with a weak exchange compared to the alkanedioate derivatives.