Bloch-Wall Phase Transition in the Spherical Model
Abstract
The temperature-induced second-order phase transition from Bloch to linear (Ising-like) domain walls in uniaxial ferromagnets is investigated for the model of D-component classical spin vectors in the limit D \to \infty. This exactly soluble model is equivalent to the standard spherical model in the homogeneous case, but deviates from it and is free from unphysical behavior in a general inhomogeneous situation. It is shown that the thermal fluctuations of the transverse magnetization in the wall (the Bloch-wall order parameter) result in the diminishing of the wall transition temperature T_B in comparison to its mean-field value, thus favouring the existence of linear walls. For finite values of T_B an additional anisotropy in the basis plane x,y is required; in purely uniaxial ferromagnets a domain wall behaves like a 2-dimensional system with a continuous spin symmetry and does not order into the Bloch one.
Cite
@article{arxiv.cond-mat/9804042,
title = {Bloch-Wall Phase Transition in the Spherical Model},
author = {D. A. Garanin},
journal= {arXiv preprint arXiv:cond-mat/9804042},
year = {2009}
}
Comments
16 pages, 2 figures