207Pb NMR study of the relaxor behavior in PbMg1/3Nb2/3O3

The local structure of the relaxer single crystal PMN has been studied via a measurement of the temperature dependences of the Pb-207 spectra and relaxation times between 450 K and 15 K. The Pb-207 NMR spectra are frequency distributions which reflect the existence of polar nanoclusters and which can be well described by the recently proposed spherical random-bond-random-field model. The temperature dependence of the Edwards-Anderson order parameter q has been determined together with the random bond coupling and the random held variance. The results agree with those obtained from the Nb-93 NMR spectra and show that at any given instant of time the crystal consists of polar clusters with variable orientation and magnitude of the local polarization. The polar clusters are on the NMR time scale 10(-4)-10(-5) s, dynamic entities which exist for a certain amount of time, disappear, and then reappear in a different form.