Uniaxially anisotropic antiferromagnets in a field on a square lattice
Institut für Theoretische Physik, Technische Hochschule RWTH Aachen, 52056 Aachen, Germany
Corresponding author: a email@example.com
Revised: 3 March 2008
Published online: 11 April 2008
Classical uniaxially anisotropic Heisenberg and XY antiferromagnets in a field along the easy axis on a square lattice are analysed, applying ground state considerations and Monte Carlo techniques. The models are known to display antiferromagnetic and spin-flop phases. In the Heisenberg case, a single-ion anisotropy is added to the XXZ antiferromagnet, enhancing or competing with the uniaxial exchange anisotropy. Its effect on the stability of non-collinear structures of biconical type is studied. In the case of the anisotropic XY antiferromagnet, the transition region between the antiferromagnetic and spin-flop phases is found to be dominated by degenerate bidirectional fluctuations. The phase diagram is observed to resemble closely that of the XXZ antiferromagnet without single-ion anisotropy.
PACS: 68.35.Rh – Phase transitions and critical phenomena / 75.10.Hk – Classical spin models / 05.10.Ln – Monte Carlo methods
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008