Multiple relaxation times in single-molecule magnets

TL;DR

This paper demonstrates that multiple relaxation times observed in single-molecule magnets can originate from intramolecular mechanisms, challenging the previous assumption that they are solely due to extrinsic factors.

Contribution

The study provides a quantum relaxation model showing intramolecular origins of multiple relaxation times in single-molecule magnets, including single-ion complexes.

Findings

Intramolecular mechanisms can produce multiple relaxation times.

Quantum relaxation equations accurately describe experimental data.

Single-ion complexes can exhibit multiple relaxation times.

Abstract

Multiple relaxation times detected in the ac magnetic susceptibility of several single-molecule magnets have been always assigned to extrinsic factors, such as nonequivalent magnetic centers or effects of intermolecular interactions in the crystal. By solving quantum relaxation equations, we prove that the observed multiple relaxation times can be of intramolecular origin and can show up even in single-ion metal complexes. For the latter a remarkably good description of the coexistent two relaxation times is demonstrated on several experimental examples. This proves the relevance of the intramolecular mechanism of multiple relaxation times in such systems, which is even easier justified in polynuclear magnetic complexes.