Tailoring symmetry groups using external alternate fields

PMMH Ecole Supérieure de Physique et Chimie Industrielles 10 rue Vauquelin, 75231 Paris Cedex 05, France

Received: 9 April 2003
Accepted: 25 June 2003

Abstract

Macroscopic systems with continuous symmetries subjected to oscillatory fields have phases and transitions that are qualitatively different from their equilibrium ones. Depending on the amplitude and frequency of the fields applied, Heisenberg ferromagnets can become XY or Ising-like —or, conversely, anisotropies can be compensated— thus changing the nature of the ordered phase and the topology of defects. The phenomenon can be viewed as an out-of-equilibrium form of order by disorder.