ANALYSIS OF MAGNETIC-RESONANCE SIGNALS FROM MIXED LATTICES WITH APPLICATION TO THE ASO44- CENTER IN THE RB-1-X(NH4)(X)H2PO4 PROTON GLASS

Electron paramagnetic resonance (EPR) signals of the AsO44- radical em bedded in the ferroelectric-antiferroelectric mixed lattice Rb-1-x(NH4 )(x)H2PO4, the so-called proton glass, exhibit unusual features: the l ine centers shift concomitant with an overall broadening, but not as p redicted by standard motional narrowing models. Earlier studies have i nterpreted this phenomenon as implying a direct evidence for the exist ence of a ''fast'' ferroelectric-antiferroelectric exchange process. I n contrast, the current work presents a phenomenological model that as cribes the observed signal to the resultant of a statistical average o f hyperfine splittings over the various possible near-neighbor interac tions, with little contribution from motional averaging or exchange pr ocesses. The methodology presented yields information on the range of interactions in a mixed lattice, and should be applicable to other rel ated cases such as NMR analysis of mixed systems.