Baxter-Wu model with fixed magnetization

We study Baxter-Wu triangular model with fixed magnetization in the framework of canonical and microcanonical ensemble, constructing the density of states by Wang-Landau algorithm. We use an approximation similar to a recently developed scheme (critical minimum energy subspace). In this scheme the sampling is not extended to the whole energy spectrum for the given magnetization but it is restricted in a properly determined part of it. We have studied lattices with linear size up to L=840. Our conclusions corroborate analogous conclusions for the square Ising model: An unconventional temperature-driven first-order phase transition take place for lattice sizes above some threshold but this transition ceases to exist at the thermodynamic limit.