The mechanism of spin-phonon relaxation in endohedral metallofullerene single molecule magnets.

This study presents the investigation of spin-phonon coupling mechanisms in fullerene-based single-molecule magnets (SMMs) using ab initio CASSCF combined with DFT calculations. While lanthanide-based SMMs, particularly those with Dy(III) ions, are known for their impressive blocking temperatures and relaxation barriers, endohedral metallofullerene (EMFs) offer a unique platform for housing low-coordinated lanthanides within rigid carbon cages. We have explored the spin dynamics in DyScS@C(82) exhibiting among the highest blocking temperature (T (B)) reported. Through our computational analysis, we reveal that while the fullerene cage enhances crystal field splitting and provides structural stability without significantly contributing to spin-relaxation driving low-energy phonons, the internal ionic motion emerges as the primary factor controlling spin relaxation and limiting blocking temperature. This computational investigation into the spin dynamics of EMF-based SMMs provides key insights into their magnetic behaviour and suggests potential strategies for improving their performance towards futuristic SMMs.