Abstract
The temperature and angular dependences of the EPR spectra of Mg[H2O]6SiF6:Mn2+ crystal were investigated in order to clarify the successive phase transitions and existence of the incommensurate phase. Five successive phase transitions were found to occur, and phase II was found to be incommensurately modulated. The modulated structure is caused mainly by the vibrational displacement of the Mg[H2O]2+ 6 ion along the c-axis. The soliton density of this phase is almost independent of temperature and remains equal to unity.