EPR evidence of local lattice mode in K3H(SO4)2 and Rb3H(SO4)2 fast-proton conductors

The observation of an anomalous temperature dependence of Mn2+ EPR spectra linewidth and nonaxial crystal-field parameter in K3H(SO4)2 and Rb3H(SO4)2 allows one to suggest the presence of “local mode” predicted by Yamada (Ferroelectrics 170 (1995) 23). The activation energy for this kind of excitation was found and equals 11.3 (0.5) and 7.4 (0.3) meV for Mn2+ doped K3H(SO4)2 and Rb3H(SO4)2, respectively.