At low temperatures, the magnetization of the molecular ferric wheel NaFe6 exhibits a step at a critical field Bc due to a field-induced level-crossing. By means of high-field torque magnetometry we observed a hysteretic behavior at the level-crossing with a characteristic butterfly shape which is analyzed in terms of a dissipative two-level model. Several unusual features were found. The non-zero bias field of the level-crossing suggests the possibility of cooling by adiabatic magnetization.
@article{arxiv.cond-mat/0210309,
title = {Butterfly hysteresis loop at non-zero bias field in antiferromagnetic molecular rings: cooling by adiabatic magnetization},
author = {O. Waldmann and R. Koch and S. Schromm and P. Müller and I. Bernt and R. W. Saalfrank},
journal= {arXiv preprint arXiv:cond-mat/0210309},
year = {2009}
}