CURIE-TEMPERATURE OF ANISOTROPIC HEISENBERG-FERROMAGNET WITH BIQUADRATIC EXCHANGE INTERACTION AND UNIAXIAL ANISOTROPY

The effects of the biquadratic exchange interaction and the uniaxial anisotropy on the Curie temperature of the ferromagnetic spin system of spin one with anisotropic exchange interaction have been calculated with the use of the pair model approximation. The dependence of the Curie temperature on the biquadratic exchange interaction and on the uniaxial anisotropy have been calculated for crystal lattices of different coordination numbers and for spin systems of various anisotropy parameters of the exchange interaction and discussed in comparative way. In a certain range of the anisotropy parameter of the exchange interaction, the biquadratic exchange interaction is shown to have no effect on the Curie temperature.