One-dimensional ferromagnetic classical-spin-field model

A continuum generalization of a one-dimensional classical ferromagnetic Heisenberg exchange-coupled spin model is solved. The field-dependent susceptibilities, specific heat, and correlation lengths are determined. The zero-field susceptibilities and correlation lengths in the presence of single-ion anisotropy energy are also calculated. The field-dependent properties are determined for the case in which the field is parallel to the single-ion anisotropy axis, and the anisotropy energy is positive. The model approximates the low-temperature behavior of the discrete spin system in the region in which spins become correlated over distances large compared to a lattice constant.