摘要:

Properties of deep level defects in polycrystalline CdS junctions were investigated using transient capacitance spectroscopy. A total of seven electron traps and one hole trap was observed with activation energies of 0.16, 0.31, 0.38, 0.42, 0.53, 0.69, 0.96, and 0.32 eV, respectively. The emission rate, capture cross section and concentration of the traps are presented. The temperature dependence of the capture cross section for the electron traps at 0.53 and 0.69 eV are also given.

ISSN:0021-8979    

DOI:10.1063/1.328249

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Nb‐based Josephson junctions are photographically fabricated with an improved lift‐off method. Aging properties of Nb/Pb junctions are studied and the possible origin of aging was pointed out, using the shape dependence andIJ‐Hcharacteristics. TheI‐Vcharacteristics of Nb/Pb junctions were analyzed quantitatively using a proximity effect model based on McMillan’s tunneling model. Maximum Josephson current was calculated incorporating the strong coupling correction. Theory and experiment agreed well for both pair and quasiparticle density of states.

ISSN:0021-8979    

DOI:10.1063/1.328250

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The dynamics of a small Josephson junction, driven either by a current source or by an external flux when the junction is the weak link element of a SQUID ring, were studied. Approximate analytical arguments and numerical simulations were used for the lumped circuit model of the junction. The various characteristic times of these devices were systematically obtained as functions of the parametersGandKof the junction and of the SQUID, respectively. The forms of the flux transitions and the times governing them are obtained for linear and periodic time variations of the external flux on the SQUID. A coupling of the SQUID to anLCcircuit was treated. Limitations on the device parameters consistent with fast response, stability, and sensitivity were obtained both for the current driven junction and for the rf SQUID.

ISSN:0021-8979    

DOI:10.1063/1.328251

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The work of Rogovin and Scalapino on noise in Josephson junctions is applied to the cases of zero‐bias junctions, forward‐biased junctions at relatively low frequencies, and to the case of arbitrary bias and frequency. In the latter case there is an infinity in the noise at the bias voltageV0=hf/2e; these quantum effects are caused by Cooper pairs. The effect appears to be measurable at 100 GHz and 2 °K, in which case the infinity in the noise occurs at 0.207‐mV bias.

ISSN:0021-8979    

DOI:10.1063/1.328252

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Microfilamentary superconducting composites of Nb3Sn fibers in bronze matrices were produced by the external diffusion method together with a solution preanneal to suppress Kirkendall porosity. The resulting materials had superior superconducting and mechanical properties at 4.2 °K, carrying overall current densities well over 104A/cm2at 15.4 T even for low (12%) superconductor fractions; over 105A/cm2at 12 T; and tolerating (in some cases) strains of the order of 2% without degradation, and stresses in the 500–1000 MPa range. There is evidence that finer superconducting filaments can tolerate much greater intrinsic strains without degradation; also, that the composites investigated were not optimized in terms of residual stresses, matrix composition, or filament spacing or size, so that further improvements are possible.

ISSN:0021-8979    

DOI:10.1063/1.328291

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The theory for the spinwave modes of a ferromagnetic single layer by Damon and Eshbach [J. Phys. Chem. Solids 19, 308 (1961)] has been extended to double layer systems. A restriction is made with respect to inplane magnetization and transverse propagation of the spinwaves. For this situation a formula is derived which predicts two surfaces modes for large film separation and one volume and one surface mode when the films are combined to a single one.

ISSN:0021-8979    

DOI:10.1063/1.328292

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Zero magnetostriction compositions in the (FeaCo1−a−bNib)100−y(Si0.4B0. 6)ysystem in the range 20⩽y⩽30 and 0⩽b⩽0.6, the resultant magnetic properties, and the crystallization temperatures were systematically studied as functions of Ni content (b) and metalloid content ( y). The iron content (a=0.058−0.11) decreases with increasing metalloid content ( y), increases with Ni content (b), and then decreases with the addition of Ni. The effects of annealing on low‐field magnetic properties were studied for two kinds of alloys; a high‐Bsalloy and a high‐&mgr; alloy. For the high‐Bsalloy, the effect of sample shape was also studied. The high remanence observed for a tape‐wound toroid and the low remanence observed for a ring‐laminated toroid in the as‐quenched state are attributed to weak uniaxial anisotropy, whose origin may be due to local tension as well as atomic and impurity arrangement introduced during the quenching. By annealing atTc<Ta<Tx , high‐&mgr; alloys with relatively lowHcandBrwere obtained.

ISSN:0021-8979    

DOI:10.1063/1.328293

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The motion equations of an infinite straight wall in a bubble garnet film are introduced for finite viscous damping. The present theory differs from previous work in assuming that the nucleated horizontal Bloch line is stable even in the Neel region of the wall. Theoretical values of the peak velocityVpand the saturation velocityV0agree fairly well with the experimental data. In‐plane field effects onVpandV0have been investigated theoretically also. When the in‐plane field is applied perpendicular to the wall plane,Vpincreases andV0decreases slightly. On the other hand,Vpdecreases andV0increases slightly due to the in‐plane field parallel to the wall.

ISSN:0021-8979    

DOI:10.1063/1.328294

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The unclamped complex dielectric constant for bismuth germanium oxide (Bi12GeO20) and bismuth germanate [Bi4(GeO4)3] has been determined at audio frequencies over the temperature range 6–325 K. For bismuth germanate, no dipolar impurities were observed. For bismuth germanium oxide, a strong dipolar impurity has been observed with an activation energy of 0.041 eV and a reciprocal frequency factor of 1.86×10−13s. The strength of the relaxation is found to be correlated with the coloration of the sample. Possible origins of the relaxation are discussed. The results for the imaginary part of the dielectric constant were used to arrive at corrected values of the real part of the unclamped dielectric constant over the full range of temperatures. While absolute values are accurate to about 1.0%, the precision of the data is better than 0.1% relative to the room‐temperature value.

ISSN:0021-8979    

DOI:10.1063/1.328295

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

In Pb(Sc0.5Ta0.5)O3it has been shown that the degree of order in the B‐site Sc3+, Ta5+cations can be controlled by suitable thermal annealing. For samples which have been well‐ordered by long annealing, dielectric measurements on single crystals show a normal first‐order ferroelectric phase change at 13 °C and a maximum low‐temperature spontaneous polarization of 23.0 &mgr;c/cm2. With increasing disorder, the crystals begin to exhibit the classical diffuse phase transition of a ferroelectric relaxor, with a broad Curie range and strong low‐frequency dielectric dispersion in the transition range. X‐ray diffraction measurements of the size of the ordered microregions suggest that ordering proceeds by different mechanisms in single‐crystal versus ceramic samples, though the resulting effects upon the dielectric behavior are very similar.

ISSN:0021-8979    

DOI:10.1063/1.328296

出版商:AIP    

年代:1980

数据来源: AIP