Abstract
It is shown that our multi-high-frequency resonant cavity technique yields distortion-free high-field electron paramagnetic resonance (EPR) spectra for single-crystal samples of the uniaxial and biaxial spin single-molecule magnets (SMM’s) and The observed line shapes exhibit a pronounced dependence on temperature, magnetic field, and the spin quantum numbers values) associated with the levels involved in the transitions. Measurements at many frequencies allow us to separate various contributions to the EPR linewidths, including significant D strain, g strain, and broadening due to the random dipolar fields of neighboring molecules. We also identify asymmetry in some of the EPR line shapes for and a previously unobserved fine structure to some of the EPR lines for both the and systems. These findings prove relevant to the mechanism of quantum tunneling of magnetization in these SMM’s.
- Received 11 December 2001
DOI:https://doi.org/10.1103/PhysRevB.65.224410
©2002 American Physical Society