Abstract
Mixed spin-1/2 and spin-1 Ising ferrimagnets on a triangular lattice with sublattices A, B, and C are studied for two spin-value distributions and by Monte Carlo simulations. The nonbipartite character of the lattice induces geometrical frustration in both systems, which leads to the critical behavior rather different from their ferromagnetic counterparts. We confirm second-order phase transitions belonging to the standard Ising universality class occurring at higher temperatures, however, in both models these change at tricritical points (TCP) to first-order transitions at lower temperatures. In the model , TCP occurs on the boundary between paramagnetic and ferrimagnetic phases. The boundary between two ferrimagnetic phases and at lower temperatures is always first order and it is joined by a line of second-order phase transitions between the paramagnetic and the ferrimagnetic phases at a critical endpoint. The tricritical behavior is also confirmed in the model on the boundary between the paramagnetic and ferrimagnetic phases.
5 More- Received 2 March 2015
DOI:https://doi.org/10.1103/PhysRevE.91.052138
©2015 American Physical Society