DFT magnetic characterization of a Fe4 SMMs series: from isotropic exchange interactions to multi-spin zero field splitting

Single molecule magnets represent one of the recent hottest research topics both at the experimental and theoretical levels. However, the tailoring of their magnetic properties is still far from being fully understood and a lot of work has to be done in order to rationalize it. In this framework, we want to present here a comprehensive magnetic characterization performed at the DFT level for a selected series of star shaped Fe-4 SMMs. In this work we have exploited the already established procedure to compute single ion anisotropy tensors to extend it in order to include the determination of exchange anisotropy tensors, both spin-spin and spin-orbit contributions, valid also for ferrimagnetic systems. In this framework, it has been possible to perform a detailed analysis of the magneto-structural correlations that govern the Fe4 family's magnetic properties. Indeed, the analysis in terms of a multi-spin Hamiltonian of the anisotropy parameters led to the conclusion that the differences in the anisotropy parameters in the Fe4 SMMs series are to be mainly ascribed to the non-collinearity and the magnitude of single ion anisotropy tensors of the peripheral ions. The results obtained at PBE and PBEO level have also been discussed.