It was noted that single crystals with the -K2SO4 structure belonged to a class of compounds which exhibited various phase transformations; including a transition into an incommensurate structure. The persistence of transition metals played an important role in the investigation of phase transformations via the ligand fields of this type of crystal; especially in the vicinity of the transition. The nature of the corresponding phase transitions was closely connected with tetrahedral complexes, [B2+X4]2-, which were bounded by A- cations. The Mn2+ ions were chosen due the persistence of the 5 external d-electrons, which were highly sensitive to the external fields.

I.Bolesta, I.Kityk, Y.Furgala, S.Velgosh: Radiation Effects and Defects in Solids, 1995, 134, 65-8