Local magnetic moments in a dinuclear Co2+ complex as seen by polarized neutron diffraction:Beyond the effective spin-(1/2) model

Polarized neutron diffraction investigations of a paramagnetic molecular dinuclear Co2+ complex, using the local site susceptibility method, show that the Co2+ ions carry opposite magnetic moments of 3.1(1) and 3.2(1) μB, making an angle of 37(1) deg. which is in agreement with the value (39 deg.) provided by the theoretical analysis of the magnetic susceptibility using the model of effective spin 1/2. Polarized neutron diffraction (PND) shows that this dinuclear Co2+ complex behaves more like a system of two antiferromagnetically coupled ions with spin 3/2, the directions of which are imposed by the distortion axis of the octahedra around each Co2+ ion due to ligand field. This first application of the local susceptibility tensor method to a molecular compound demonstrates the efficiency of the PND method as a tool for exploring magnetic anisotropy in molecular paramagnets.