Functional Dependence of Magnetic Anisotropy Parameters in Dy(III) Metallocene Single-Ion Magnets

The dependence of the magnetic anisotropy parameter (D) on density functional theory (DFT) exchange–correlation functionals was systematically investigated for Dy(III) metallocene single-ion magnets (SIMs). Pure generalised gradient approximation (GGA) functionals, such as BLYP and PBE, reproduce the negative sign of the experimental D values. In contrast, both adiabatic (global) and range-separated (RS) hybrid functionals containing Hartree-Fock (HF) exchange tend to yield positive D values. By introducing a small fraction (5–10%) of HF exchange into the BLYP functional, the calculated D values show good agreement with the experimental data for all complexes. These results indicate that pure GGA functionals are effective in describing the “local” exchange interactions governing magnetic anisotropy, while the inclusion of a small amount of exact “non-local” exchange can partially compensate for the limitations of GGA functionals. This behaviour highlights the importance of the subtle balance between 4f-orbital localisation and metal–ligand hybridisation in predicting the magnetic properties of Dy(III) metallocene complexes.