Magnetic phase transitions and the dynamic electric polarization in the LaMn$_{2}$O$_{5}$ compound

Possible phase transitions to the ferromagnetic phase in the LaMn$_{2}$O$_{5}$ compound have been studied in the framework of a phenomenological approach based on a symmetry analysis. The conditions that parameters of the thermodynamic potential must satisfy to realize a second-order transition have been found. The line of the first-order phase transitions in this system and the critical point of the second-order phase transition line have been determined. It was shown that a dynamic electric polarization can form in the antiferromagnetic phase.