Phase states of an S=1 magnet with anisotropic exchange interactions

A system with anisotropic Heisenberg and biquadratic exchange interactions and with easy-plane single-ion anisotropy is investigated. The magnons' spectra are obtained and investigated in various phase states of the system. The free energy density is analyzed, and the system's phase diagrams are built. The limiting cases of the Ising ferromagnet and the magnet with an isotropic exchange interaction are considered. The temperature phase transition into paramagnetic state for one-, two- and three-dimensional magnets is investigated.