Interacting boson approach to the static properties of classical ferromagnetic chains in applied field

Abstract

An interacting spin wave theory is presented for describing the temperature behaviour of the thermodynamical quantities of classical ferromagnetic Heisenberg chains in an applied field. An explicit expression for the Green function of the longitudinal magnetisation fluctuation is given and longitudinal susceptibility correlation length and magnetisation are evaluated. The inadequacy of a naive Hartree-Fock renormalisation and the determinant role of the thermal activated spin-energy coupling are shown.