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Hamburg 2001 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 8: Relaxoren und heterogene Systeme

DF 8.1: Hauptvortrag

Donnerstag, 29. März 2001, 14:30–15:10, S18/19

NMR in Relaxors and Dipolar Glasses — •Robert Blinc — J. Stefan Institute, University of Ljubljana, Ljubljana, Slovenia

The local structure of ferroelectric relaxors and dipolar glasses is characterized by the local polarization distribution function W(p) and its moments which can be probed by the quadrupole perturbed NMR frequency ν or chemical shift of a given nucleus. The NMR lineshape is a frequency distribution f(ν) which reflects W(p). Comparison of theoretical and experimental data for f(ν) yields the local structure of disordered systems and allows for the determination of the Edwards-Anderson order parameter. Different forms of W(p) are obtained for Ising-type dipolar glasses, quadrupolar glasses, inhomogeneous ferroelectrics or spherical glass systems. We report on the 207Pb, 45Sc, and 93Nb NMR spectra of the perovskite relaxor single crystals PbMg1/3Nb2/3O3, PbSc1/2Nb1/2O3 and PbSc1/2Ta1/2O3. Comparison with the 87Rb, 2H, and 31P NMR lineshapes of the deuteron glass Rbx(ND4)1−xD2PO4 shows that perovskite relaxors can be described as spherical glasses, whereas deuteron glasses are Ising-type glasslike. In both cases the random bonds dominate the random fields.

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