Spontaneous magnetization of the O(3) ferromagnet at low temperatures
Abstract
We investigate the lowtemperature behavior of ferromagnets with a spontaneously broken symmetry O(3)>O(2). The analysis is performed within the perspective of nonrelativistic effective Lagrangians, where the dynamics of the system is formulated in terms of Goldstone bosons. Unlike in a Lorentzinvariant framework (chiral perturbation theory), where loop graphs are suppressed by two powers of momentum, loops involving ferromagnetic spin waves are suppressed by three momentum powers. The leading coefficients of the lowtemperature expansion for the partition function are calculated up to order p^{10}. In agreement with Dyson's pioneering microscopic analysis of the cubic ferromagnet, we find that, in the spontaneous magnetization, the magnonmagnon interaction starts manifesting itself only at order T^{4}. The striking difference with respect to the lowtemperature properties of the O(3) antiferromagnet is discussed from a unified point of view, relying on the effective Lagrangian technique.
 Publication:

Physical Review B
 Pub Date:
 March 2002
 DOI:
 10.1103/PhysRevB.65.094430
 arXiv:
 arXiv:condmat/0106492
 Bibcode:
 2002PhRvB..65i4430H
 Keywords:

 75.40.Cx;
 75.30.Ds;
 12.39.Fe;
 11.10.Wx;
 Static properties;
 Spin waves;
 Chiral Lagrangians;
 Finitetemperature field theory;
 Condensed Matter;
 High Energy Physics  Phenomenology
 EPrint:
 23 pages, 4 figures