Two-dimensional anisotropic Heisenberg antiferromagnet in a field

Holtschneider, M., Selke,W., Leidl, R.
Institut für Theoretische Physik, Technische Hochschule Aachen,
D-52056 Aachen, Germany


The classical, square lattice, uniaxially anisotropic Heisenberg antiferromagnet in amagnetic field parallel to the easy axis is studied using Monte Carlo techniques. The model displays a long-range ordered antiferromagnetic, an algebraically ordered spin-flop, and a paramagnetic phase. The simulations indicate that a narrow disordered phase intervenes bewteen the ordered phases down to quite low temperatures. Results are compared to previous, partially conflicting findings on related classical models as well as the quantum variant with spin S=1/2.