摘要:

Aperture fields in the diffraction by a slit was studied numerically and experimentally. Numerical calculations are based on the exact solution in the form of an infinite series of Mathieu functions. Experimental measurements, by means of a parallel‐plate device, of the field distribution over the aperture in slits of 3.5&lgr;, 3&lgr;, 2.21&lgr;, 1.27&lgr; width (&lgr;=wavelength) are discussed, and show satisfactory agreement with the exact solution for slits of width 1.27&lgr; and 2.21&lgr;. The exact solution of diffraction by a slit due to a line source is also presented in the Appendix.

ISSN:0021-8979    

DOI:10.1063/1.1735438

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Measurements of the sensitivity of grain‐boundary photodetectors indicate an expected minimum detectable power of better than 10−14w. Major factors governing the sensitivity are the minority carrier lifetime and the distance of the boundary from the irradiated surface. Spectral measurements show an added absorption edge response at about 1.67 &mgr; and 1.72 &mgr;. This added response could be caused by deep‐lying acceptor levels or by excitons with a long lifetime. However, the experimental evidence points to direct absorption at the grain boundary as the most likely reason for the absorption edge irregularities.

ISSN:0021-8979    

DOI:10.1063/1.1735439

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Approximation formulas for the surface excesses of carriers at large values of the reduced surface and bulk potentials are derived, and computed results are presented.

ISSN:0021-8979    

DOI:10.1063/1.1735440

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Magnetic anisotropy has been observed in evaporated Permalloy films deposited at oblique incidence of the vapor. Electron micrographs of such films reveal chains of crystallites whose long axes are oriented perpendicular to the vapor beam. A ``self‐shadowing'' model is proposed to explain chain growth, i.e., the area behind a crystallite is left vacant because it is in the crystallite's shadow. Oriented crystallite chains are thus caused by a purely geometric process; their existence has also been demonstrated for Au, Pt, W, and Mg. Oriented chains give rise to a number of macroscopic effects: magnetic anisotropy, anisotropic resistance, dichroism, and anisotropic resonance linewidth. Experiments involving the stripping of oblique‐incidence Permalloy films from their substrates indicate the presence of an anisotropic strain which, in conjunction with magnetostriction, gives another contribution to the magnetic anisotropy; this contribution explains the observed compositional dependence of the magnetic anisotropy. Surface tension, which tends to contract the crystallite chains, is postulated as the generating force of anisotropic strain; surface tension could similarly generate the isotropic strain which is found in normal‐incidence films.

ISSN:0021-8979    

DOI:10.1063/1.1735441

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The intermediate phases TiFe, TiCo, and TiNi have been investigated by x‐ray powder diffraction techniques. The atomic arrangements of these ensembles have been determined to be of the cesium chloride, B2 type. Monochromatic x radiation was utilized in the investigation.

ISSN:0021-8979    

DOI:10.1063/1.1735442

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Components in a complex primary recrystallization texture, which is a matrix texture for secondary recrystallization to the Goss texture in 3% silicon‐iron strip, have been determined by the axis‐chart method of Jetter, McHargue, and Williams. The results obtained are compared with former pole‐figure results and found to include components not previously resolved or noted. It is found also that the components of the texture explain reasonably well the observed magnetic torque curve of the material.

ISSN:0021-8979    

DOI:10.1063/1.1735443

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Using a simple extension of standard magneto‐ionic theory, the frequency dependence of the complex Hall field is calculated for samples with rectangular, cylindrical, and spherical geometry. The result has application to ``open‐circuit'' Hall effect measurements on semiconductors at microwave frequencies.

ISSN:0021-8979    

DOI:10.1063/1.1735444

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The fast neutron irradiation behavior of germanium and silicon Esaki diodes has been experimentally examined. The dominant change produced is an increase in the ``excess'' current which is proportional to integrated neutron flux. The observed increase in the vicinity of the current minimum is approximately 2.6×10−15amp/fast neutron and 1.1×10−14amp/fast neutron for germanium and silicon diodes respectively. Substantial changes result in the voltage‐current characteristics of the diodes employed in the decade of exposure between 1016–1017fast neutrons/cm2for germanium diodes and between 1015–1016fast neutrons/cm2for silicon diodes. One kilomegacycle cavity oscillators employing germanium diodes exhibit a marked reduction in power output in the decade of exposure between 1016–1017fast neutrons/cm2. The magnitude of the decrease is in approximate agreement with the observed bombardment reduction of diode negative conductance.

ISSN:0021-8979    

DOI:10.1063/1.1735445

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The off‐resonance microwave absorption (subsidiary absorption) which frequently occurs at high‐microwave power and which may exist even in the absence of an external dc magnetic field has been used to observe the interaction between the magnetic flux reversal and the microwave loss processes in polycrystalline ferrite. These experiments have shown that the spin waves associated with high‐power, off‐resonance microwave absorption have a negligible effect on the flux reversal process. However, the flux reversal process has a marked effect on the high‐power microwave loss. During the flux reversal process, this high‐power, off‐resonance microwave absorption was found in some cases to be negligible.

ISSN:0021-8979    

DOI:10.1063/1.1735446

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The bending strength of glass slides, which had the dimensions 38×6×0.16 mm, was measured at different relative pressures of water vapor. The adsorption isotherms of water vapor on powdered glass, which had the same composition as the slides, were measured in a separate experiment. The reduction of the surface free energy as function of the vapor pressure was calculated from the isotherms. The observed variation of the strength was compared with the strength variation calculated from the reduction of the surface free energy. The Griffith equation for brittle fracture was used to relate strength and surface free energy. Two cases were considered: (1) the specimens were weakened by the reduction of the surface free energy and (2) the specimens were weakened by the reduction of the surface free energy and by a deepening of the surface cracks. Both interpretations agreed with the experimental results because, by using the Griffith equation, only the lower limits for the strength of the specimens could be calculated.It was found that the observed strength did not decrease steadily with increasing vapor pressure, but had a secondary maximum at a relative pressure of about 0.2. The maximum reduction of the strength corresponding to complete wetting with water was already reached at a relative pressure of about 0.5. The ratio of the strength in saturated water vapor to the strength in vacuum was found to be independent of the surface damage of the specimens.

ISSN:0021-8979    

DOI:10.1063/1.1735447

出版商:AIP    

年代:1960

数据来源: AIP