RESUMEN
The critical properties of the spin-1 Blume-Capel model in two dimensions is studied on Voronoi-Delaunay random lattices with quenched connectivity disorder. The system is treated by applying Monte Carlo simulations using the heat-bath update algorithm together with single histograms re-weighting techniques. We calculate the critical temperature as well as the critical exponents as a function of the crystal field Δ. It is found that this disordered system exhibits phase transitions of first- and second-order types that depend on the value of the crystal field. For values of Δ≤3, where the nearest-neighbor exchange interaction J has been set to unity, the disordered system presents a second-order phase transition. The results suggest that the corresponding exponent ratio belongs to the same universality class as the regular two-dimensional ferromagnetic model. There exists a tricritical point close to Δt=3.05(4) with different critical exponents. For Δt≤Δ<3.4 this model undergoes a first-order phase transition. Finally, for Δ≥3.4 the system is always in the paramagnetic phase.
RESUMEN
We study the phase diagram in the H-T plane of the potassium jarosite compound KFe(3)(OH)(6)(SO(4))(2) for the antiferromagnetic XY model with Dzyaloshinskii-Moriya (DM) interaction using the mean-field theory for different value of DM. In our approach, we obtain the tricritical point in the H-T plane and the adjustment has a strong correlation with experimental data.
