45Sc NMR study of the relaxor transition in a lead scandotantalate single crystal

The relaxer transition in a disordered lead scandotantalate "virgin" single crystal has been studied by measuring the Sc-45 NMR spectra and spin-lattice relaxation rates. The observed spectra can be decomposed in a narrow 1/2--> - 1/2 central part and a broad background due to the satellite transitions. The data demonstrate that the macroscopic cubic symmetry is locally broken and thar the Sc electric quadrupole coupling constant amounts to about 12 MHz. The local polarization distribution function and the temperature dependence of the Edwards-Anderson order parameter have been determined and can be well described by the recently proposed spherical random bond-random field model.