Abstract
A methodology for investigating dynamics of various spin probes in mixed/glassy systems of the KH2PO4 type is developed. Using this methodology, electron spin resonance (ESR) features of the AsO44- centre in the paraelectric phase of Rb1-x(NH4)xH2PO4 are shown to arise from strain-broadening and motional-broadening effects. These conclusions are in disagreement with those of a recent study, which implicated the various features observed in the existence of ferroelectric-antiferroelectric fluctuations in Rb1-x(NH4)xH2PO4. It is additionally shown that hyperfine couplings from Rb isotopes make the dominant contribution to the ESR spectra in Rb-containing compounds.