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.