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Owing to advances in synchrotron sources and instrumentation for x-ray spectroscopy and scattering it is becoming feasible to probe directly the electronic states responsible for ferroelectricity. As an example we show that polarized XANES measurement proved that in PZN-PT the polarization of Nb is negligibly small, and the most of polarization is carded by Pb. We also demonstrate that the orbital characteristics of the Nb-O bonding in KNbO[sub 3] can be detemfined by the anomalous x-ray scattering measurement. [ABSTRACT FROM AUTHOR]

The atomic structure of Pb(Zr, Ti)O[sub 3] solid solutions near the morphotropic phase boundary (MPB) was examined using time-of-flight neutron diffraction. In addition to the conventional crystallographic refinement the atomic pair distribution function (PDF) analysis was used. Crystallographic analysis suggests that the average structure changes significantly through the MPB. However, the PDF analysis, which is more accurate in describing the local structure, shows that changes are more gradual. In particular the PDF suggests that the local environment of each element remains relatively invariant of composition. Ti is always ferroelectrically active, while Zr is not. Pb is always displaced against oxygen atoms and forms short bonds at about 2.45 Å. What changes most with the Ti/Zr ratio is the distribution in the direction of Pb displacement. It is suggested that the population of local Pb displacements changes between <100> and <110> in the pseudocubic notation with the Ti/Zr ratio, and the MPB is a crossover point with maximum disorder. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Near the metal-insulator transition competing forces to localize and delocalize charges are in delicate balance, and small perturbations can produce drastic effects. For the manganites that show colossal magnetoresistivity (CMR) the electron-lattice interaction plays a key role in producing and altering the balance through formation of polarons. Our recent measurements of high-energy LO phonons by inelastic neutron scattering demonstrate that polaronic charge localization tendency exists also in the cuprates that exhibit high-temperature superconductivity (HTSC). It is suggested that the lattice is an integral part of the HTSC mechanism, and that marginal stability of polaron is important for the CMR effect in manganites as ell as for the HTSC in cuprates. [ABSTRACT FROM AUTHOR]

In spite of the success of electron theories to account for the ferroelectric phenomena, ideas in classical crystal chemistry are still useful in unraveling complex behavior of multicomponent solids. In particular they provide a natural explanation of high susceptibilities of mixed-ion systems based upon the concept of competing interactions. However, they are largely phenomenological and empirical. It is suggested that the concept of atomic level stresses can bridge the gap between the crystal chemistry approach and first-principle calculations in a most meaningful way. Also some novel experimental methods, which directly probe certain aspects of the electronic state relevant for this phenomenon, are discussed. [ABSTRACT FROM AUTHOR]