O. Waldmann, C. Dobe, S. T. Ochsenbein, H. U. Güdel and I. Sheikin
Field-Induced Magnetoelastic Instabilities in Antiferromagnetic Molecular Wheels
Phys. Rev. Lett. 96, 027206/1-4 (2006)                 

Abstract: The magnetic torque of the antiferromagnetic molecular wheel CsFe₈ was studied down to 50 mK and up to 28 T. Below about 0.5 K phase transitions were observed at the field-induced level crossings (LCs). Intermolecular magnetic interactions are very weak excluding field-induced magnetic ordering. A magnetoelastic 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.