Phase Transitions and Magnetic Structures in the Antiferromagnetic Potts Model

The antiferromagnetic 3-state Potts model on a body-centered cubic lattice with competing interactions of the first (J1) and second (J2) nearest-neighbor was studied by the Monte Carlo method. A phase diagram of the critical temperature dependence on the value J2 was constructed. The competition of exchange interactions in the range -2/3 < J2 < 0 was determined to result in a phase separation and a change in the phase transition order. In the low-temperature region, an ordered phase, lying inside a partially disordered phase with broken sublattice symmetry, was found. In addition, at J2 -2/3, a phase with broken sublattice symmetry state of a different type arises. The magnetic structures of the ground state corresponding to different regions of the phase diagram were established.