An X Ray analysis on the Pb-Bi system from pure Pb ton Pb 30 at. % Bi yields both phase and lattice constant. Tc and Hall constant were also measured. The samples were thin films.Se presenta un estudio estructural mediante rayos X de la aleacion PbBi desde Pb puro hasta Pb 30% at. % Bi lo que brinda la fase y el parametro de red. Tambien se determino la temperatura de transicion a superconductividad de estas aleaciones y se midio el efecto Hall en peliculas delgadas.

This paper describes a flexible MOS transistor layout generator which draws optimal layouts whatever the W and L dimensions. The drawing methodology is based on the use of small elementary parts, called bricks, which are placed side by side inside a user-specified boundary. The generated transistors may allow diffusion merging along whichever sides the user wishes and may have a global rectilinear shape. The internal structure of these cells may also be chosen by the designer so that it is well suited to his application. Transistors developed using this generator have been tested, and have been used to build a simple operational amplifier.

Complex dielectric response measurements have been made on a C60/C70 mixture pellet. The frequency and temperature ranges cover from 20 Hz to 1 MHz and from 30 to 300 K. Results show that the real part of the dielectric constant is 5 with a weak thermally activated polarization contribution. This thermal polarization is believed to be related to reorientation of C60 molecules recently observed by many techniques such as NMR, sound velocity, thermal conductivity, and others. Our data yield relaxation frequencies for reorientation, indicating that the presence of an additional electric dipole moment of the orientationally ordered C60 molecules at low temperature contributes 0.2–0.3 to the static dielectric constant.

This paper describes a flexible analog cell generator which is integrated in a complete automatic layout system for analog circuits. It can generate an optimal layout for any W and L dimensions. The generated cells may allow diffusion merging along some sides and may have a global rectilinear shape. They also allow over-the-cell routing if the net is not too noisy. fashion. We have tried to make the generator as flexible as possible in order to be easily used by the other two tools. One of its originalities is the possibility to generate non rectangular transistors that can fit better in any layout. Results of devices characterization will be shown at the end of this paper together with the layout of an operational amplifier made of these transistors.

We have magnetically characterized single crystal Fe3O4/NiO superlattices grown on MgO(001), where the layer thickness has been varied over a wide range. Hysteresis for modulation wavelength Λmod = 258 Å is similar to bulk Fe3O4, while loops for Λmod < 80 Å are nearly linear with applied field with minimal hysteresis and remanence. The magnetization slopes of the latter are roughly proportional to Λmod, and increase from 5 to 300 K. Measurements above 300 K suggest that both exchange coupling across NiO/Fe3O4 interfaces and strain-induced variations in anisotropy, rather than paramagnetism, lead to this linear behavior.

Dielectric constants from 10(2) to 10(6) are found in room-temperature, ceramic, nonmetallic YBa2CU3O6+delta (delta approximately 0-0.4). The frequency, temperature, and electric-field dependencies of the dielectric response, as well as the quasistatic current-voltage behavior of this material, are reported. We show that the high polarizability is tied to a short (less-than-or-equal-to 100 angstrom) length scale, persists to microwave frequencies, and is accompanied by a strong electric-field dependence.

The dielectric permittivity of Fe3O4/NiO superlattices reveals frequency-dependent features, not found in the constituent materials, which we identify as due to interfacial (Maxwell-Wagner) electrical polarization. Large modulations of the displacement field within 34 angstrom of an interface have thus been observed. We find further evidence that the low-frequency dielectric constant is half the value and the interfacial relaxation time is approximately 10 times larger in a 34 angstrom/34 angstrom superlattice than expected suggesting that the short superlattice wavelength is less than the length scale required to define "bulk" polarization and conductivity.

The authors present CLAP, a program for automatic layout generation of a cascode current source. The source is considered as a parameterized macrocell whose parameters are either the dimensions of the transistors or the values of the expected currents and voltages. The layout may be drawn by assembling the transistors using analog techniques like abutment or by employing a specific compact configuration called `imbricated S'. A description of the software and some layouts obtained are given

High quality Fe3O4/NiO multilayered structures with nominal artificial periodicity 17 Å/ 17 Å and 34 Å/34 Å have been made by molecular beam epitaxy. The conductivity of the modulated structures is orders of magnitude higher for current parallel to the layers than for the transverse direction, reaching a ratio of 106−a value which is comparable with the largest known anisotropy for any material. This strong anisotropy shows that a like modulation of electrical conductivity has been achieved over distances as small as tens of Å and also suggests the possibility of voltage controlled superlattice phenomena.

We have investigated the magnetic order, using SQUID magnetometry, for short modulation wavelength Fe3O4/NiO superlattices, grown on single crystal MgO. Ferrimagnetic Fe3O4 has a saturation moment of ∼500 emu/cm3 at 0 K and a Curie temperature of 858 K, while bulk NiO is antiferromagnetic with a Néel temperature of 525 K. Very high crystalline quality with little interdiffusion is indicated by X-ray diffraction, SEM, optical microscopy, and in-situ RHEED, and the samples show highly anisotropic electrical conductivity which also indicates the strong modulation present. Long wavelength samples (Λmod > 200 Å) have a behavior only slightly different from that expected from bulk Fe3O4, but for Λmod<80 Å, spontaneous magnetization is replaced by paramagnetism, with weak temperature dependence (not I/T) from 5 K to 400 K.

A large and strongly temperature-dependent static dielectric constant \ensuremath{\kappa} is found in the high-temperature (T>900 \ifmmode^\circ\else\textdegree\fi{}C) phase of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathrm{x}}$. Values of \ensuremath{\kappa} from \ensuremath{\sim}30 at 4.3 K to \ensuremath{\sim}700 at 290 K have been measured in samples quenched from 950 \ifmmode^\circ\else\textdegree\fi{}. Some consequences of the ferroelectriclike polarizability in the phase which precedes the metallic/superconducting phase are noted.

A first order-like phase transition at Tp = 900°C in YBa2Cu3Ox followed by a second order transition from 900 to 600°C is found to be responsible for the high temperature superconductivity. Samples quenched from above Tp are not superconducting and have a tetragonal unit cell. Samples quenched from Tp down to 600°C show a continuously increasing and sharpening superconducting transition, and a continuously growing orthorhombic distortion. From the quenching and anneal/recovery studies we concluded that a thermodynamically inhomogeneous state occurs below Tp.

Superconductivity, with onet at 50 K and a transition width of about 30 K, has been observed in a multiphase mixture with composition Y1Ba2Ag3Ox. About 30% of the sample excludes flux in ac inductance measurements. The probable absence of a localized moment and large valence fluctuations in this material has implications for some current theories of high temperature superconductivity.

A phase transition starting at 900\ifmmode^\circ\else\textdegree\fi{}C has recently been found to be a necessary precursor to the high-${T}_{c}$ superconductivity in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{x}$. We report here that the phase change involves an insulator ($T>900\ifmmode^\circ\else\textdegree\fi{}$C phase) to metal transformation. Specific-heat measurements show that both phases have comparable Debye temperatures, and, unexpectedly, linear $T$ terms at low temperature. For the insulating phase, this term is comparable to that in a transition metal. The insulating phase also has an electrical resistivity of the unusual form $\ensuremath{\rho}\ensuremath{\propto}{e}^{\ensuremath{-}\frac{T}{{T}_{a}}}$ below 300 K.

The torsional modulus of ${\mathrm{Y}}_{1}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{9\ensuremath{-}x}$, measured by the composite oscillator method, shows a softening of \ensuremath{\simeq}1% on cooling through the superconducting transition. The change is 3 to 4 orders of magnitude larger than that in an average modulus for a typical superconductor. For the high symmetry implied by our polycrystalline sample, furthermore, no change is allowed by symmetry for this mode at the superconducting (or any Landau-type) transition. The decrease in modulus is accompanied by an increase in damping.