Monte Carlo Study of Mixed-Spin S=(1/2,1) Ising Ferrimagnets

Selke, W., Oitmaa, J.
School of Physics, University of New South Wales, Sydney, Australia; Institut für Theoretische Physik, Technische Hochschule Aachen, D-52056 Aachen, Germany


We investigate Ising ferrimagnets on square and simple--cubic lattices with exchange couplings between spins of values S=1/2 and S=1 on neighbouring sites and an additional single--site anisotropy term on the S=1 sites. Based mainly on a careful and comprehensive Monte Carlo study, we conclude that there is no tricritical point in the two--dimensional case, in contradiction to mean-field predictions and recent series results. However, evidence for a tricritical point is found in the three--dimensional case. In addition, a line of compensation points is found for the simple--cubic, but not for the square lattice.