71 research outputs found
Outward potassium current oscillations in macrophage polykaryons: extracellular calcium entry and calcium-induced calcium release
Cosmogenic Be and He accumulation in pleistocene beach terraces in death valley california U.S.A.: implications for cosmic-ray exposure dating of young surfaces in hot climates
Nanodomain patterns in ultra-tetragonal lead titanate (PbTiO<sub>3</sub>)
Very recently, the discovery of ultra-tetragonal PbTiO3 thin films was reported [Zhang et al., Science, 361, 494 (2018)], in which the switchable out-of-plane polarization was seen to be almost twice that of any previously known ferroelectric. To understand more about this system and to explore features that might contribute to these remarkable functional properties, we have mapped the polarization microstructure on the nanoscale using piezoresponse force microscopy (PFM) (scan sizes less than 700 nm). Our study reveals an extremely fine-scale pattern, with individual domains typically 20-50 nm in size, all of which exhibit both out-of-plane and in-plane polarization components. In-plane vector PFM polarization maps show strongly charged quadrant-lattice domain arrays with fourfold domain wall junctions (vertices). The existence of fourfold vertices in ferroelectrics is rare but can be explained via the "Ashkin-Teller"model, in which very large interfacial lattice mismatch strains and local electric fields play a role. This ultra-tetragonal ferroelectric system was expected to contain straightforward c-axis out-of-plane 180° domains, but instead shows an extremely rich nanoscale domain tiling pattern; these unusual nanodomains may be important in facilitating the extremely high switchable polarization values previously reported.</p
Proton excitation of 1 states in Pb and a lower limit on the strength of the isoscalar spin-flip part of the effective nucleon-nucleon interaction
Isovector and isoscalar spin-flip excitations in even-even s-d shell nuclei excited by inelastic proton scattering
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