PHASE-TRANSITION IN A NONEQUILIBRIUM 2D DEGENERATE SYSTEM

This letter analyzes how an external field opposing the attainment of thermodynamic equilibrium affects a 2D magnetic material with n-compon ent spins (n greater than or equal to 2). In a nonequilibrium system w ith a purely dissipative dynamics, there is a second-order phase trans ition accompanied by the onset of a spontaneous magnetization. This be havior is different from that in an equilibrium degenerate magnetic ma terial. The nonequilibrium phase transition falls in the universality class of an equilibrium transition in a uniaxial ferroelectric. The ph ase diagram of the system is analyzed. (C) 1995 American Institute of Physics.