The mean field phase diagrams of YbIG

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Abstract
The existence of the symmetry allowed magnetic phases in ferrimagnetic YbIG is discussed. The continuous and quasi‐continous transformations of these phases are treated using the thermodynamic potential expansions whose coefficients are determined from the well known effective spin Hamiltonian of Yb ions. The special cases with the magnetic field H along the , and symmetry directions are dealt with. The existence of a low symmetry phase connected with the occurrence of a tetracritical point is stated for H ∥ . The collinear‐canted phase transition is of the first order for H ∥ but at high fields quasi‐continuous with a very narrow metastability region. An isolated critical point, in which three first‐order and two second‐order transition lines meet, is found on this first‐order phase boundary. The connection with the Potts model is outlined. The calculated phase diagrams are compared with experimental results.