P. Santini et al., CLASSICAL FLUCTUATIONS AND ANISOTROPY IN QUASI-ONE-DIMENSIONAL ANTIFERROMAGNETS, Physical review. B, Condensed matter, 54(9), 1996, pp. 6327-6332
The magnetization of the easy-plane quasi-one-dimensional antiferromag
nets CsMnBr3 and RbMnBr3 in the presence of an external magnetic field
can be well interpreted by minimizing the classical magnetic energy.
However, this type of calculation cannot reproduce the observed anisot
ropy of the magnetization at high magnetic fields, which therefore is
usually attributed to quantum effects. We show that the anisotropy is
already present at the classical level, provided thermal fluctuations
are taken into account.