The Semi-Infinite Anisotropic Spin-i Heisenberg Ferromagnet

A. Benyoussef；A. Boubekri；H. Ez-Zahraouy；M. Saber

Chinese Journal of Physics

37卷1期（1999 / 02 / 01）

89 - 97

英文

Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions, the phase transitions in the semi-infinite anisotropic spin-i Heisenberg ferromagnet on a simple cubic lattice are examined. For fixed values of the reduced exchange anisotropic parameter, the critical temperature of the system is studied as a function of the ratio R of the surface exchange couplings to the bulk ones. It was found that if R ≤ R,, the system orders at the bulk critical temperature Tc^B / J and if R ≥ Rc, the system exhibits two successive transitions. The surface orders at the surface critical temperature Tc^S / J which is higher than Tc^B / J and as the temperature is lowered, in the presence of an ordered surface, the bulk orders at Tc^B / J.