Manifestation of Spin Selection Rules on the Quantum Tunneling of Magnetization in a Single Molecule Magnet

TL;DR

This study demonstrates how molecular symmetry and Jahn-Teller axis orientations influence quantum tunneling of magnetization in a Mn3 single-molecule magnet, revealing symmetry-imposed selection rules affecting tunneling behavior.

Contribution

It provides experimental evidence linking molecular symmetry and Jahn-Teller axes to quantum tunneling selection rules in SMMs, highlighting factors affecting tunneling processes.

Findings

Quantum tunneling occurs only at elevated temperatures between excited states with spin differences multiple of three.

Symmetry forbids tunneling from the lowest metastable state, explained by Jahn-Teller axes orientation.

Transverse dipolar fields influence tunneling, emphasizing their importance in SMM behavior.

Abstract

We present low temperature magnetometry measurements on a new Mn3 single-molecule magnet (SMM) in which the quantum tunneling of magnetization (QTM) displays clear evidence for quantum mechanical selection rules. A QTM resonance appearing only at elevated temperatures demonstrates tunneling between excited states with spin projections differing by a multiple of three: this is dictated by the C3 symmetry of the molecule, which forbids pure tunneling from the lowest metastable state. Resonances forbidden by the molecular symmetry are explained by correctly orienting the Jahn-Teller axes of the individual manganese ions, and by including transverse dipolar fields. These factors are likely to be important for QTM in all SMMs.