摘要:

An expression for the optimum discharge parameters of beam‐plasma ion sources is obtained and compared with experimental data.

ISSN:0021-8979    

DOI:10.1063/1.325020

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The electron density distribution is determined for a low‐pressure gas in a conical plasma tube. The distribution is found to vary in the radial direction as a spherical Bessel function and in the &Vthgr; direction as a Legendre polynomial, the order of which is proportional toL/a.

ISSN:0021-8979    

DOI:10.1063/1.325021

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

An expression for the electron temperature in a medium‐pressure radio‐frequency flowing positive column plasma has been derived for a cylindrical discharge tube. The effect of flow on electron temperature increases as the product of gas pressure and tube radius decreases.

ISSN:0021-8979    

DOI:10.1063/1.325022

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Two different stationary regimes for roll instabilities in homeotropically oriented samples of nematic liquid crystals are observed. The roll pattern can develop parallel or perpendicular to the applied shear depending on the frequency of the imposed stress.

ISSN:0021-8979    

DOI:10.1063/1.325023

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We report the preparation of thin films of gallium phosphide and gallium nitride by deposition from low‐pressure rf‐excited plasmas in mixtures of trimethylgallium with ammonia and phosphine, respectively. With the deposition conditions used, the gallium phosphide is found to be amorphous, while the gallium nitride is polycrystalline. We present preliminary measurements of optical and electrical properties.

ISSN:0021-8979    

DOI:10.1063/1.325024

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A series of photovoltaic heterojunctions of the typen‐Zn0.1Cd0.9S/p‐CdTe have been prepared by spray pyrolysis of ZnCdS films on single‐crystal CdTe with variation of the CdTe substrate temperature and of the postdeposition heat‐treatment temperature in hydrogen. Open‐circuit voltages as high as 0.82 V are observed compared to maximum values of 0.74 V observed forn‐CdS/p‐CdTe junctions also prepared by spray pyrolysis. Cell efficiencies are in the 6–8&percent; range without correction for reflection losses.

ISSN:0021-8979    

DOI:10.1063/1.325025

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

In the early 1960’s one-dimensional model systems were regarded as amusing toys with the advantage of being far more easily solvable than their ’’real’’ three-dimensional counterparts. Now essentially 1-D (quasi-1-D) magnets can be ’’tailor-made’’ in the laboratory. Even more popular is the field of organic conductors like TTF⋅TCNQ, which are naturally quasi-1-D. Currently solitons and related solutions of non-linear, dispersive 1-D differential equations are ubiquitous in physics, including the area of 1-D magnetism. These developments are discussed in the Introduction. The rest of this paper is concerned with model Hamiltonians, model comparisons, critical singularities in 1-D (quasi-1-D) systems, accuracy of numerical techniques in comparison with exact solutions, brief accounts of dilute and disordered 1-D systems, and 1-D spin dynamics. Finally, a comment is made on a variety of interesting isomorphisms between 1-D magnets and phenomena in several other areas of physics, for example 2-D ferroelectrics, field-theoretic models, and realistic fluids. Comparison of theory and experiment has been the subject of several excellent reviews and is therefore not discussed here.

ISSN:0021-8979    

DOI:10.1063/1.325026

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A number of experiments on magnetic insulating systems is reviewed which bear upon the following subjects: (i) the magneticXYmodel, (ii) the quadratic Heisenberg magnet, (iii) magnetic double‐layers, (iv) lattice‐dimensionality crossovers, (v) singlet–ground state systems, (vi) magnetic systems doped with magnetic or nonmagnetic impurities.

ISSN:0021-8979    

DOI:10.1063/1.325027

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Over the last years a considerable number of effects have been found in Rare‐Earth (RE) systems which are caused by the crystalline–electric field (CEF) splitting of the RE‐ions. This splitting is usually of the order of 1–100 cm−1and involves the ground stateJ‐multiplet of the incomplete 4f‐shell. A discussion will be given of some of the observed phenomena by using simple physical arguments. One group of effects concerns the influence of the CEF‐split ions on the transport properties of conduction electrons in case the matrix is metallic. The behavior of the thermoelectric power is here of special interest. Furthermore if the matrix is a superconductor the CEF‐splitting shows up in the ability of the RE‐ions to suppress superconductivity. A second group of effects concerns the coupling of lattice deformations (phonons) to CEF‐levels. Special attention will be paid to phenomena which involve an applied magnetic field. Examples are the Faraday rotations of the phonon‐polarization vectors or the Cotton‐Mouton effect. Analogous effects occur for optical phonons. They can be detected by Raman‐scattering experiments.

ISSN:0021-8979    

DOI:10.1063/1.325028

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Relations between two‐dimensional physical systems, continuous‐spin Hamiltonians, and discrete spin or Potts models are established by Landau symmetry and renormalization‐group arguments. Experimental realizations ofXYand Heisenberg models with cubic anisotropy as well as of different Potts models are reviewed. Then a unified model encompassing these classes of models is introduced. For the special case of a six‐state discrete model a phase diagram is proposed based on duality and Migdal renormalization‐group transformations.

ISSN:0021-8979    

DOI:10.1063/1.325029

出版商:AIP    

年代:1978

数据来源: AIP