EPR spectroscopy of some Mn2+ doped langbeinites with regard to low temperature phases

Electron paramagnetic resonance (EPR) spectra of Mn2+ centers in 11 langbeinites, A(2)(+)B(2)(2+)(SO4)(3)(2-), with A(+) = NH4+, K+, Rb+ or Tl+ and B2+ = Mg2+, Ca2+, Zn2+ or Cd2+ are measured over relatively large temperature ranges chosen to cover phase transitions, if any. For 7 langbeinites which do not contain Mg2+, phase transitions are observed, but no more than one low temperature phase is distinguishable by EPR. Except for the K-Zn langbeinite, only one defect center is noticeable in that phase. The low temperature EPR parameters are reported, and their temperature dependence is discussed with respect to correlations between structure and phase transition characteristics and to the trigger mechanism.