Abstract
High-frequency electron paramagnetic resonance (HFEPR) and alternating current (ac) susceptibility measurements are reported for a new high-symmetry complex, . The results are compared to those of other high-symmetry spin single-molecule magnets (SMMs), including the original acetate, , and the and complexes. These comparisons reveal important insights into the factors that influence the values of the effective barrier to magnetization reversal, , deduced on the basis of ac susceptibility measurements. In particular, we find that variations in can be correlated with the degree of disorder in a crystal which can be controlled by desolvating (drying) samples. This highlights the importance of careful sample handling when making measurements on SMM crystals containing volatile lattice solvents. The HFEPR data additionally provide spectroscopic evidence suggesting that the relatively weak disorder induced by desolvation influences the quantum tunneling interactions and that it is under-barrier tunneling that is responsible for a consistent reduction in that is found upon drying samples. Meanwhile, the axial anisotropy deduced from HFEPR is found to be virtually identical for all four complexes, with no measurable reduction upon desolvation.
- Received 5 May 2009
DOI:https://doi.org/10.1103/PhysRevB.80.094408
©2009 American Physical Society