摘要:

The composition and conduction of silicon nitride film formed by the reaction of SiH2Cl2and NH3at a low pressure were studied. In the range investigated, this film is amorphous N‐rich silicon nitride no matter what the growth conditions. Conduction at room temperature in a steady state was investigated by analyzing the charge distribution without using an average field approximation. Probable charge distribution in the nitride was derived from the thickness dependence of the applied voltage at a constant current and from the flat‐band voltage shift giving the interface fields. When current densityJ= 10−5A/cm−2, we obtainednt(0) = 3×1018cm−3, interface fieldsEs= 4.0×106V/cm, and the charge centroid &ohgr; = 210 A˚. The dynamic dielectric constant is calculated as &egr;d= 3.9 from the temperature dependence of conduction, using the average field approximation. The average field approximation is valid only at high temperatures.

ISSN:0021-8979    

DOI:10.1063/1.329920

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Discontinuity in the resonant voltage (traveling wave resonance) as a function of applied magnetic field has been observed in large Josephson tunnel junctions. It is believed that our results can be explained in terms of peculiar magnetic properties of large junctions of finite lengthL≫&lgr;J, i.e., the quantization of internal fields and magnetic hysteresis. The discontinuity corresponds to the change of number of vortices penetrating the junction barrier. The experimental voltage jumps are in fairly good agreement with these calculated from the theory.

ISSN:0021-8979    

DOI:10.1063/1.329921

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

ac losses of superconducting solenoidal coils were investigated with a calorimetric method while applying a current or uniform magnetic field of 50 Hz with a sinusoidal wave form. The peak value of the ac current was varied from 0 to 15 rms A and that of the ac magnetic field from 0 to 0.02 T. These experimental conditions are for a practical regime where loss theories are difficult to apply and empirical data of the type generated are directly useful. Nine coil samples of various sizes were constructed with different fine multifilamentary superconducting wires. The ac losses observed are proportional to the square of the amplitude of an applied ac magnetic field or an applied ac current and appear to be mainly eddy current losses. The ac losses of coils of the same size caused by an applied ac current were the same regardless of the kind of wire used. All losses in the superconducting coils appeared to be equivalent to those expected from eddy currents in solid copper wires 0.72 times the diameter of the wires used, independent of the wire size and internal configuration.

ISSN:0021-8979    

DOI:10.1063/1.329922

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

This paper is an elaboration upon Tucker’s quantum theory of mixing, which has proven very valuable in interpreting recent experiments in superconducting quasiparticle mixing. Tucker’s formula for the conversion gain of a three‐frequency quantum mixer in the low intermediate frequency (IF) limit is generalized to include arbitrary source reactance; one choice of source reactance is found to resonate out the quantum reactance in the conversion expression. The signal reflection gain is evaluated; it becomes infinite simultaneously with the IF conversion gain. Infinite gain occurs only within the region of negative dc differential resistance. A number of relationships among the complex elements of the small‐signal admittance matrix is presented; the nonlinear reactive elements are shown to be small under certain conditions when the conversion gain is maximized. The local oscillator (LO) power required for quantum mixing is calculated and found to be related to the gain denominator. This implies that certain quantum mixers at high gain will exhibit a constant gain‐powerwidth product and a gain‐proportional noise temperature component. A particularly simple expression for the conversion gain of an optimized quantum mixer is developed, which agrees with previous experiments. The origin of nonclassical behavior, including conversion gain and the nonlinear quantum reactance, is discussed. We conclude that the nonlinear quantum reactance, though it certainly must exist, is not itself responsible for conversion gain and has a minor, perhaps insignificant, effect upon the properties of a quantum mixer.

ISSN:0021-8979    

DOI:10.1063/1.329923

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The present work reports the theoretical considerations of the magnetocrystalline anisotropy of ferrous ions induced by tetravalent dopants in yttrium iron garnet. Using the spin Hamiltonian developed earlier by us and the molecular field (h) approximation we derive the cubic anisotropy constantsK1andK2at zero temperature. We adopt the Alben’setal. model of twelve inequivalent Fe2+sites in silicon‐substituted yttrium iron garnet. Results are given forh= 400, 300, 200 and the spin Hamiltonian parameters with the trigonal &Dgr; = 300, 400, 500, 600, 700 and the nontrigonal crystal field parameter &Ggr; = 200, 300 cm−1. The agreement with the experimentalK1andK2is quite good. The discussion reveals that the properties of the far and near sites in the two‐center model can now be theoretically explained. The theoretical ratios ofK1(far) toK1(near) agree well with experiment. Thus our results speak in favor of the orbital singlet rather than the doublet model assumed previously for Fe2+in silicon‐ or germanium‐substituted yttrium iron garnets.

ISSN:0021-8979    

DOI:10.1063/1.329924

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Magnetostriction constants &lgr;111have been determined at room temperature with the double‐crystal x‐ray diffraction technique by measuring a small change in the lattice parameter. Measurements were carried out for epitaxial garnet films of Y3Fe5O12and Sm0.85Tm2.15Fe5O12grown on [111] oriented Gd3Ga5O12substrates; and also for flux‐grown bulk single crystal of Y3Fe5O12. Values of &lgr;111obtained were −1.7×10−6for film and −3.0×10−6for bulk crystal. &lgr;111of Sm0.85Tm2.15Fe5O12was −5.0×10−6. The discrepancy in &lgr;111values between film and bulk Y3Fe5O12is almost accounted for by the fact that the film can deform only perpendicular to the film plane due to the shear force of the substrate. It has been experimentally demonstrated that &lgr;111does not depend on film thickness or lattice mismatch, which is consistent with the present analysis.

ISSN:0021-8979    

DOI:10.1063/1.329925

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The magnetization characteristics of a nickel thin film deposited onto a glass substrate with oblique incidence are studied by the measurement of its extraordinary Hall effect (spin Hall effect). The results show that the Hall loop which corresponds to theM‐Hloop is anisotropic with respect to the direction of the applied field, and that the loop varies from normal type to anomalous type reversibly with the angle between the applied fieldHand the film normal in a plane containing both the film normal and the easy axis.

ISSN:0021-8979    

DOI:10.1063/1.329926

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The model of Mopsik and Broadhurst for piezoelectricity in polymer electrets is reconsidered and further developed. The main features of the model are reviewed with particular attention directed to tensorial aspects of the piezoelectric effect. A characteristic difference is pointed out in the patterns of piezoelectric response attributed to two distinct sources: (1) the strain dependent residual polarization associated with the alignment of electric dipoles, and (2) the presence of trapped charge injected during the poling process. Trapped charge contributes to the piezoelectric shear stress constantse15,e24whereas the oriented dipoles do not (unless electrostrictive anisotropy is important).

ISSN:0021-8979    

DOI:10.1063/1.329927

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Thermal diffusivities of metals can be accurately measured by the photoacoustic method. It is necessary, however, to use rear‐surface illumination and to work at sufficiently high modulation frequency. Furthermore, to prevent mechanical vibrations of the sample due to its periodic dilatation (’’drum effect’’), this sample must be carefully fixed on the backing.

ISSN:0021-8979    

DOI:10.1063/1.329966

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Photoacoustic detection technique is employed to investigate two‐photon absorption (TPA) effects in ZnS over a wide frequency range with polarized 5 nsec dye laser pulses. By analyzing the dispersion and polarization dependence of TPA, we find that near the band gap, the TPA in ZnS occurs via allowed‐forbidden type one‐step, two‐photon transitions.

ISSN:0021-8979    

DOI:10.1063/1.329967

出版商:AIP    

年代:1982

数据来源: AIP