EPR study of the phase transition in [N(CH3)4]2ZnCI4doped with Mn2+ions

The successive phase transitions of [N(CH3)4,]2ZnCl4 have been investigated by means of EPR and DSC of Mn2+ doped samples. Changes in the EPR spectrum with varying temperature show the presence of six phases (I, II, …, VI) between 27 and −140°C. The spin Hamiltonian parameters and the orientations of the D tensor were determined in phases I and V. In phase II, the broadening and splitting of the spectrum are attributed to incommensuration. A discommensurate phenomenon is also detected. The spectra in phases III, IV and VI, are characteristic of modulated superstructures. The modulation amplitude and orientation angle for ZnCl2- 4 ion are related to the phase angle. The effect of changing temperature on the modulation amplitude and initial phase are shown.