A Binuclear Fe(III)Dy(III) Single Molecule Magnet. Quantum Effects and Models

The binuclear [FeIII(bpca)(μ-bpca)Dy(NO3)4], having Single Molecule Magnet (SMM) properties, belonging to a series of isostructural FeIIILnIII complexes (Ln = Eu, Gd, Tb, Dy, Ho) and closely related FeIILnIII chain structures, was characterized in concise experimental and theoretical respects. The low temperature magnetization data showed hysteresis and tunneling. The anomalous temperature dependence of Mössbauer spectra is related to the onset of magnetic order, consistent with the magnetization relaxation time scale resulting from AC susceptibility measurements. The advanced ab initio calculations (CASSCF and spin−orbit) revealed the interplay of ligand field, spin−orbit, and exchange effects and probed the effective Ising nature of the lowest states, involved in the SMM and tunneling effects.