We study the phase diagram and multicritical behavior of anisotropic Heisenberg antiferromagnets on a square lattice in the presence of a magnetic field along the easy axis. We argue that, besides the Ising and XY critical lines, the phase diagram presents a first-order spin-flop line starting at T=0, as in the three-dimensional case. By using field-theory methods, we show that the multicritical point where these transition lines meet cannot be O(3) symmetric and occurs at finite temperature. We also predict how the critical temperature of the transition lines varies with the magnetic field and the uniaxial anisotropy in the limit of weak anisotropy.
Multicritical behavior of two-dimensional anisotropic antiferromagnets in a magnetic field
VICARI, ETTORE
2007-01-01
Abstract
We study the phase diagram and multicritical behavior of anisotropic Heisenberg antiferromagnets on a square lattice in the presence of a magnetic field along the easy axis. We argue that, besides the Ising and XY critical lines, the phase diagram presents a first-order spin-flop line starting at T=0, as in the three-dimensional case. By using field-theory methods, we show that the multicritical point where these transition lines meet cannot be O(3) symmetric and occurs at finite temperature. We also predict how the critical temperature of the transition lines varies with the magnetic field and the uniaxial anisotropy in the limit of weak anisotropy.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.