Magnetic Field-Controlled Phase Transitions in Antiferromagnetic Structures

The properties of an antiferromagnetic substance are investigated in the presence of a magnetic field. Analytical expressions are obtained in terms of the mean-field approximation. An external magnetic field is shown to be non-destructive to the phase transition in the antiferromagnetic substance. It only changes critical exponents and shifts the critical point. This allows us to control the critical properties of the system. The number of critical points can vary from one (the second-order phase transition) to four (two first-order phase transitions and two second-order phase transitions). It is shown that variations in the magnetic field magnitude can raise the critical temperature by three-odd times in materials with strong antiferromagnetic interactions. A Monte Carlo simulation carried out for a three-dimensional lattice with a finite interaction radius substantiates that the action of an external field brings about a shift in the temperature of the transition. The simulation results agree well with the analytical expressions of the mean field theory.