Comment on the Antiferromagnetic-Paramagnetic Phase Transition in Nonzero Field

Abstract

The concept of higher-order transition is analyzed and the reasons for generally believing that a transition of order higher than 2 does not exist are reviewed. This analysis is applied to the results of Landau et al. on dysprosium aluminum garnet (DAG) and it is shown with and without the magnetic field $H$, the antiferromagnetic transition is likely to have the same behavior provided that $H$ is less than its value at the tricritical point. At the tricritical point itself, a different behavior appears.