The spin-s quantum Heisenberg ferromagnetic models in the physical magnon theory

The spin-s quantum Heisenberg ferromagnetic model is investigated in the physical magnon theory. The effect of the extra unphysical magnon states on every site is completely removed in the magnon Hamiltonian and during approximation procedure so that the condition = 0(n greater than or equal to 2s + 1) is rigorously satisfied. The physical multi-approximation occupancy (1 less than or equal to n less than or equal to 2s) is proportional to T-3n/2 at low temperature and is equivalent to 1/(2s + 1) at the Curie temperature. The magnetization not only unified but also well-behaved from zero temperature to Curie temperature is obtained in the framework of the magnon theory for the spin-s quantum Heisenberg ferromagnetic model. The ill-behaved magnetizations at high temperature in earlier magnon theories are completely corrected. The relation of magnon (spin wave) theory with spin-operator decoupling theory is clearly understood. (C) 2001 Elsevier Science B.V. All rights reserved.