RESUMO
Neutron inelastic scattering measurements of the polar transverse optic phonon mode dispersion in the cubic relaxor Pb(Zn(1/3)Nb(2/3))0.92Ti0.08O3 at 500 K reveal anomalous behavior in which the optic branch appears to drop precipitously into the acoustic branch at a finite value of the momentum transfer q = 0.2 A(-1) measured from the zone center. We speculate that this behavior is the result of nanometer-sized polar regions in the crystal.
RESUMO
We report on the phase diagram for charge-stripe order in La1.6-xNd0. 4SrxCuO4, determined by neutron and x-ray scattering studies and resistivity measurements. From an analysis of the in-plane resistivity motivated by recent nuclear-quadrupole-resonance studies, we conclude that the transition temperature for local charge ordering decreases monotonically with x, and hence that local antiferromagnetic order is uniquely correlated with the anomalous depression of superconductivity at x approximately 1 / 8. This result is consistent with theories in which superconductivity depends on the existence of charge-stripe correlations.
