Possibility for Direct Observation of Order Parameter Suppression in Cuprate/Manganite Spin-Injection Heterostructures
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Cuprate/Manganite Spin-Injection Heterostructures↗
Engineering topics
Vasquez, R. P.
Publications and source records attributed to Vasquez, R. P..
Doping Dependence of the Giant Spontaneous Hall Effect in La(1-x)Ca(x)Co0(3) (x=.1-0.5)
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Giant Spontaneous Hall Doping↗
Tunneling Evidence of Half-Metallic Ferromagnetism in La(0.7)Ca(0.3)MnO(3)
Direct experimental evidence of half-metallic density of states (DOS) is observed by scanning tunneling spectroscopy on ferromagnetic La(0.7)Ca(0.3)MnO(3) which exhibits colossal magnetoresistance (SMR).
optical imaging↗
X-Ray Photoemission Measurements of La(1-x)Ca(x)CoO3(x = 0, 0.5)
X-ray photoemission measurements of the core levels and valence electronic structure of LaCoO3 and La(0.5)Ca(0.5)CoO3 high quality epitaxial films are presented. Shifts of the core levels and main valence band features are consistent with a doping-induced change in the chemical potential. Oxygen states are found to significantly contribute to a peak in the valence band at 1 eV binding energy, verifying earlier results of cluster calculations. A Fermi level crossing of this same band upon doping is observed, yielding a high Fermi level density of states.
Vasquez, R. P.↗
Modeling and Optimization of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applicaitons
The development of a YBa(sub 2)Cu(sub 3)O(sub 7-(kronecker delta))(YBCO) hot-electron bolometer (HEB) quasioptical mixer for a 2.5 heterodyne receiver is discussed. The modeled device is a submicron bridge made from a 10 nm thick film on a high thermal conductance substrate. The mixer performance expected for this device is analyzed in the framework of a two-temperature model which includes heating both of the electrons and the lattice. Also, the contribution of heat diffusion from the film through the substrate and from the film to the normal metal contacts is evaluated....a single sideband temperature of less than 2000k is predicted.
tetrahertz hot-electron bolometer quasioptical mix↗
Electronic Structure of Tl2Ba2CuO(6+Delta) Epitaxial Films Measured by X-Ray Photoemission
The valence electronic structure and core levels of Tl2Ba2CuO(6 + delta) (Tl-2201) epitaxial films have been measured with X-ray photoelectron spectroscopy and are compared to those of Tl2Ba2CaCu2O(8 + delta) (Tl-2212). Changes in the Tl-2201 core-level binding energies with oxygen doping are consistent with a change in the chemical potential. Differences between the Tl-2201 and Tl-2212 measured densities of states are consistent with the calculated Cu 3d and Tl 6s partial densities of states.
Vasquez, R. P.↗
Improved Fabrication of High-Temperature Superconducting-Normal-Superconducting (SNS) Josephson Junctions for Device Applications
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large critical currents substrate material silicon↗
Development of a High-Tc Hot-Electron Superconducting Mixer for Terahertz Applications
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quasioptical YBCO hot-electron bolometer mixer YBC↗
Fabrication of High-T(sub c) Hot-Electron Bolometric Mixers for Terahertz Applications
Superocnducting hot-electron bolometers (HEB) represent a promising candidate for heterodyne mixing at frequencies exceeding 1 THz. Nb HEB mixers offer performance competitive with tunnel junctions without the frequency limit imposed by the superconducting energy gap.
HEB heterodyne heterodyne receivers↗
Lattice Distortion, Polaron Conduction, and Jahn-Teller Effect on teh Magnetoresistance of La(sub 0.7)Ca(sub 0.5)CoO(sub 3) Epitaxial Films
In summary, we have investigated the role of lattice distortion, polaron conduction and Jahn-Teller coupling in the occurrence of the colossal negative magnetoresistance in perovskite oxides. We conclude that larger lattice distortion gives rise to larger zero-field resistivity and larger magnitude of negative magnetoresistance.
colossal negative magnetoresistance CMR lattice di↗
Electronic Structure of T1(sub 2)BA(sub 2)CuO(sub 6+delta) Epitaxial Films Measured by X-ray Photoemission
In summary, the valence electronic structure and core levels of T1-2201 epitaxial films have been measured in this work with XPS.
superconducting cuprates transition temperatures p↗
Anomalous Hall Effect in a Feromagnetic Rare-Earth Cobalite
Rare-Earth manganites and cobalites with the perovskite structure have been a subject of great recent interest because their electrical resistance changes significantly when a magnetic field is applied...we have studied the Hall effect in thin film La(sub 0.5)Ca(sub 0.5)CoO(sub 3) material and have obtained convincing evidence fo the so called anomalous Hall effect, typical for magnetic metals...Our results suggest that near the ferromagnetic ordering temperature, the dominant electron scattering mechanism is the spin fluctuation.
manganites cobalites perovskite structures magneti↗
Electronic Structure of La(sub 1-x)Ca(sub x)CoO(sub 3) (x = 0, 0.5)
X-ray photoemission measurements of the core levels and valence electronic structure of LaCoO(sub 3) and La(sub 0.5)Ca0.5CoO(sub 3) high quality epitaxial films are presented. Shifts of the core levels and main valence band features are consistent with a doping-induced change in the chemical potential.
epitaxial films Fermi level↗
Correlation of the Lattice Distortion and Polaron Conduction with the Physical Properties of La (sub 0.7)Ca(sub 0.3)MnO(sub 3) and La(sub 0.5)Ca(sub 0.5)CoO(sub 3) Epitaxial Films
The effects of lattice distortion on the physical properties of La (sub 0.7)Ca(sub 0.3)MnO(sub 3) and La(sub 0.5)Ca(sub 0.5)CoO(sub 3) films are investigated. Our results suggest that larger substrate-induced lattice distortion gives rise to larger zero-field resistivity and larger negative magnetoresistance.
lattice distortion epitaxial films lattice polaron↗
Infrared Optical Properties of La(sub 0.7)Ca(sub 0.3)MnO(sub 3) Epitaxial Films
The reflectance of La(sub 0.7)Ca(sub 0.3)MnO(sub 3) epitaxial films on perovskite substrates with a range of lattice constants is studied in the frequency range of 50 cm(sup -1) - 5000cm(sup -1). The complex dielectric functions of the bare La(sub 0.7)Ca(sub 0.3)MnO(sub 3) films are obtained by modeling the measured reflectivity spectra of the two-layer La(sub 0.7)Ca(sub 0.3)MnO(sub 3)/substrate system with separaately measured dielectric functions of the bare substrate.
lattice distortion epitaxial films lattice polaron↗
Effects of Lattice Distortion and Jahn-Teller Coupling on the Magnetoresistance of La(sub 0.7)Ca(sub 0.3)MnO(sub 3) and La(sub 0.5)Ca(sub 0.5)CoO(sub 3) Epitaxial Films
Studies of La(sub 0.7)Ca(sub 0.3)MnO(sub 3) epitaxial films on substrates with a range of lattice constants reveal two dominant contributions to the occurence of colossal negative magnetoresistance (CMR) in these manganites:...We therefore suggest that lattice polaron conduction associated with Jahn-Teller coupling is essential for the occurence of CMR, and that lattice distortion further enhances the CMR effect in the manganites.
lattice distortion epitaxial films lattice polaron↗
Electronic Structure of TIBa(sub 2)CaCu(sub 2)O(sub 7-delta)
The core levels of TIBa(sub 2)CaCu(sub 2)O(sub 7-delta) epitaxial films have been measured with x-ray photoelectron spectroscopy (XPS). The valence electronic structure has been determined using the full-potential linear muffin tin orbital band structure method and measured with XPS.
Epitaxial films van Hove Fermi level↗
Electronic Structure of HgBa2CaCu2O(6+delta) Epitaxial films measured by x-ray Photoemission
The electronic structure and chemical states of HgBa2CaCu20(sub 6 + delta), epitaxial films have been studied with x-ray photelectron spectroscopy. Signals from the superconducting phase dominate all the core-level spectra, and a clear Fermi edge is observed in the valence-band region. The Ba, Ca, Cu, and O core levels are similar to those of Tl2Ba2CaCu208(+)O(sub 6 + delta), but distinct differences are observed in the valence bands which are consistent with differences in the calculated densities of states.
Vasquez, R. P.↗