Spin-Peierls instabilities of antiferromagnetic rings in a magnetic field
journal contributionposted on 2018-08-09, 09:09 authored by Valeria Lante, Ioannis RousochatzakisIoannis Rousochatzakis, Karlo Penc, O Waldmann, Frederic Mila
Motivated by the intriguing properties of magnetic molecular wheels at field-induced level crossings, we investigate the spin-Peierls instability of antiferromagnetic rings in a field by exact diagonalizations of a microscopic spin model coupled to the lattice via a distortion-dependent Dzyaloshinskii-Moriya interaction. We show that, beyond the unconditional instability at level crossings for infinitesimal magnetoelastic coupling, the model is characterized by a stronger tendency to distort at higher level crossings and by a dramatic angular dependence with very sharp torque anomalies when the field is almost in the plane of the ring. These predictions are shown to compare remarkably well with available torque and nuclear magnetic resonance data on CsFe8. © 2009 The American Physical Society.
This work was supported by the Swiss National Fund, by MaNEP, by the Hungarian OTKA Grants No.K62280 and No.K68807, and the ESF HFM project (Exchange Grant 1273).