Classical limit of the Heisenberg model

Abstract

The proper way to take the classical limit of the Heisenberg model is demonstrated. It is shown that a mixing of quantum-mechanical and classical formulas can give unphysical results. Some examples show the need for the proper way to take the classical limit. The validity of various conclusions concerning the temperature dependence of the spin-wave damping arrived at from the first few frequency moments is also discussed for the classical Heisenberg linear chain.