Fluctuations in anisotropic magnetic superconductors

Fluctuations of the magnetic order parameter in anisotropic magnetic superconductors are studied within a model with (a) an easy-magnetization axis, and (b) a minimum of the reciprocal susceptibility $\omega \left(\overrightarrow{\mathrm{q}}\right)$ on a ring in the reciprocal space. Both the quartic and the sixth-order terms in the free-energy functional are included. The model is studied in $d\ge 3$ dimensions, and the phase diagram is proposed. Fluctuations in real magnetic superconductors such as Er${\mathrm{Rh}}_4$ ${\mathrm{B}}_4$ and Ho${\mathrm{Mo}}_6$ ${\mathrm{S}}_8$ are discussed.