Classical Ferromagnetic Heisenberg Chain in a Magnetic Field

Abstract
The dynamics of classical ferromagnetic Heisenberg chains in a magnetic field is investigated. Contrary to previous theories, in the longitudinal spectral shapes temperature is found to play a crucial role through a dynamical spin-energy coupling whose effect is competitive with the field. Thermal disorder ultimately causes a nearly isotropic situation, leading to a new interpretation of the features of recent computer experiments.