LATTICE-STRAIN VERSUS DYNAMIC EFFECTS IN ELECTRON-SPIN-RESONANCE STUDIES OF RB1-XNH4XH2PO4 - COMMENT

A methodology for investigating dynamics of various spin probes in mix ed/glassy systems of the KH2PO4 type is developed. Using this methodol ogy, electron spin resonance (ESR) features of the AsO4(4-) centre in the paraelectric phase of Rb1-x(NH4)xH2PO4 are shown to arise from str ain-broadening and motional-broadening effects. These conclusions are in disagreement with those of a recent study, which implicated the var ious features observed in the existence of ferroelectric-antiferroelec tric fluctuations in Rb1-x(NH4)xH2PO4. It is additionally shown that h yperfine couplings from Rb isotopes make the dominant contribution to the ESR spectra in Rb-containing compounds.