Field-induced magnetoelastic instabilities in antiferromagnetic molecular wheels

TL;DR

This study investigates the magnetic and elastic behavior of the CsFe8 molecular wheel at very low temperatures and high magnetic fields, revealing phase transitions at level-crossings and demonstrating a magneto-elastic instability.

Contribution

It introduces a generic model showing that antiferromagnetic molecular wheels are unconditionally unstable at level-crossings, explaining experimental torque data.

Findings

Phase transitions observed at 0.5 K at level-crossings

Weak intermolecular interactions exclude magnetic ordering

Model predicts magneto-elastic instability at level-crossings

Abstract

The magnetic torque of the antiferromagnetic molecular wheel CsFe8 was studied down to 50 mK and in fields up to 28 T. Below ca. 0.5 K phase transitions were observed at the field-induced level-crossings (LCs). Intermolecular magnetic interactions are very weak excluding an explanation in terms of field-induced magnetic ordering. A magneto-elastic coupling was considered. A generic model shows that the wheel structure is unconditionally unstable at the LCs, and the predicted torque curves explain the essential features of the data well.