Materials Literature
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The optimized effective potential (OEP) method allows for calculation of the local, effective single particle potential of density functional theory for explicitly orbital-dependent approximations to the exchange-correlation energy functional. In the present work the OEP method is used together with the approximation…
We have prepared a number of GaAs structures delta-doped by Sn using the well-known molecular beam epitaxy growth technique. The samples obtained for a wide range of Sn doping densities were characterised by magnetotransport experiments at low temperatures and in high magnetic fields up to 38 T. Hall-effect and Shubni…
We describe instrumentation for conducting high sensitivity millimeter-wave cavity perturbation measurements over a broad frequency range (40-200 GHz) and in the presence of strong magnetic fields (up to 33 tesla). A Millimeter-wave Vector Network Analyzer (MVNA) acts as a continuously tunable microwave source and pha…
Effects of electron correlation on the electronic structure and magnetic properties of the Gd(0001) surface are investigated using of the full-potential linearized augmented plane wave implementation of correlated band theory ("LDA+U"). The use of LDA+U instead of LDA (local density approximation) total energy calcula…
We have studied the superconducting behavior of 100 nm Titanium Nitride (TiN) thin film in a perpendicular magnetic field. We found a zero field transition temperature of 4.6 K and a slope in the H-T plane of -0.745 T/K. At 4.2 K, we have performed careful transport measurements by measuring both the differential resi…
Recently a new monoclinic phase in the PbZr(1-x)TixO3 ceramic system has been reported by Noheda et al. for the composition x= 0.48. In the present work, samples with Ti contents of x= 0.47 and 0.50, which are both tetragonal below their Curie points, have been investigated. In the sample with x= 0.50, the tetragonal…
The synthesis of bulk amounts of high quality single-walled carbon nanotubes (SWNTs) is accomplished by optimizing the chemical compositions and textural properties of the catalyst material used in the chemical vapor deposition (CVD) of methane. A series of catalysts are derived by systematically varying the catalytic…
Diffractive optical elements (DOEs) are characterized by a large negative dispersion. This property can be exploited to correct chromatic aberration in hybrid optical systems. The diffraction efficiency of phase DOEs decreases when the wavelength deviates from the design wavelength. Consequently, DOEs are usually appl…
We report x-ray absorption spectra of high temperature solid Pd at 1770 K, liquid Pd at 1850 K, and undercooled liquid Pd at 1770 and 1670 K (about 160 K below ${T}_{m}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1827\mathrm{K}$). Data of excellent quality were collected at the European Synchrotron Radiation Fac…
The magnetic properties of free ${\mathrm{Gd}}_{N}$ clusters ( $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}13$, 21, and 22) have been measured between 90 and 600 K in a Stern-Gerlach experiment. ${\mathrm{Gd}}_{13}$ and ${\mathrm{Gd}}_{21}$ are found to be superparamagnetic (SP) whereas ${\mathrm{Gd}}_{22}$ i…
The damage of Pb(Zr0.53Ti0.47)O3 thin film due to dry etching process was characterized in terms of the microstructure and electrical properties. The damaged layer seems to be amorphous and the thickness of the damaged layer is about 10 nm. The existence of such a layer in Pt/Pb(Zr0.53Ti0.47)O3/Pt ferroelectric capaci…
The dependence of polarization switching on thermal histories has been investigated for K1+-modified lead zirconate titanate (PZT) ceramics by Sawyer–Tower polarization methods. It was found that double-loop-like polarization characteristics in the aged condition could be reversed to normal single loop polarization ch…
A fundamental issue in ferroic systems (ferromagnetic and ferroelectric) is the scaling of the order parameter (magnetization or polarization) with size. Specifically, in ferroelectric thin films, deviations in the polarization can occur due to: (i) competition between thermal vibrations and the correlation energy (wh…
Perovskite Ba0.5Sr0.5TiO3 thin films have been synthesized on (001) LaAlO3 substrates by pulsed laser ablation. Extensive x-ray diffraction, rocking curve, and pole-figure studies suggest that the films are c-axis oriented and exhibit good in-plane relationship of 〈100〉BSTO//〈100〉LAO. Rutherford backscattering spectro…
The experimental evidence for orbital ordering in ${\mathrm{LaMnO}}_{3}$ and ${\mathrm{La}}_{0.5}{\mathrm{Sr}}_{1.5}{\mathrm{MnO}}_{4}$ is critically reexamined in the light of realistic calculations based on multiple scattering theory and finite difference method for the resonant x-ray scattered intensity at a forbid…
We studied ${\mathrm{Mn}}_{12}$-acetate by inelastic neutron scattering and diffraction. We separated the energy levels corresponding to the splitting of the lowest $S$ multiplet ( $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}10$ ground state). The irregular spacing of the transition energies unambiguously sho…
In layered manganites with orbital and charge orderings, the degeneracy of the Mn $4p$ orbitals as well as the $3d$ ones is lifted by the effects of the $4p$ bands and the local Coulomb interactions. We formulate the atomic scattering factor for the resonant x-ray scattering in the memory function method by taking int…
We report the synthesis and characterization of Nd0.5Sr0.5MnO3 thin films grown by the pulsed laser deposition technique on [100]-oriented LaAlO3 substrates. X-ray diffraction (XRD) studies show that the films are [101] oriented, with a strained and quasi-relaxed component, the latter increasing with film thickness. W…
A formulation of variational principles in terms of functional integrals is proposed for any type of local plastic potentials. The minimization problem is reduced to the computation of a path integral. This integral can be used as a starting point for different approximations. As a first application, it is shown how t…
Highly-ordered arrays of parallel carbon nanotubes were grown by pyrolysis of acetylene on cobalt within a hexagonal close-packed nanochannel alumina template at 650 °C. The nanotubes are characterized by a narrow size distribution, large scale periodicity, and high densities. Using this method ordered nanotubes with…