摘要:

The effect of the magnetocrystalline anisotropy on the resonance of the saturation magnetization vanishes in single‐crystal spheres of YIG for a continuous multiplicity of crystalline directions which form a cone about each ⟨100⟩. Consequently, the resonance shift caused by the change of anisotropy with temperature is eliminated when the external magnetic field coincides with any direction lying on this cone. It is shown that deviations from the ideal alignment become inconsequential if they occur in predictable crystallographic planes tangent to this contour.

ISSN:0021-8979    

DOI:10.1063/1.1714354

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Combined x‐ray topographic and ultramicroscopic studies have shown a one‐to‐one correspondence between dislocation lines and chains of submicroscopic light‐scattering bodies within a magnesium oxide crystal in the ``as‐received'' state. Dislocations with any orientation and Burgers' vector were found to be decorated. The geometry and Burgers' vectors of various unusual dislocation configurations have been determined. These special configurations all arose from the extension of edge segments in the course of intense dislocation climb combined with a strong preference for a line orientation parallel to a cube direction. The relationship of such configurations to the general distribution of dislocations showed that the epoch of intense dislocation climb had occurred late in the evolution of the dislocation distribution. X‐ray diffraction evidence on whether the climb was due to the absorption of interstitials or of vacancies is as yet inconclusive.

ISSN:0021-8979    

DOI:10.1063/1.1714355

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Experimental arrangements and procedures in the Matteucci‐effects study of ferromagnetics for the case of dynamic torsion in alternating or in direct magnetic fields are described.

ISSN:0021-8979    

DOI:10.1063/1.1714356

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

60Co gamma irradiation ofp‐type silicon produces donors in the lower half of the forbidden gap. From the temperature dependence of the electrical properties, a level 0.35 eV above the valence band was located for the case of silicon pulled from silica crucibles. For the case of float‐zone silicon, two levels 0.21 and 0.28 eV above the valence band were found. The 0.35‐eV level is introduced at the rate of 10−4net donors/cm3per photons/cm2. The introduction rate for the 0.21‐eV level is lower than that for the 0.35 level, and that for the 0.27‐eV level is so low that it was difficult to measure.

ISSN:0021-8979    

DOI:10.1063/1.1714357

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Fox and Li first calculated mode shapes in Fabry‐Perot‐type oscillators assuming a passive homogeneous medium between the mirrors. In laser oscillators the gain is strongly depressed by saturation in regions where the amplitude of the mode is large, thus giving a nonuniform gain distribution in the cavity. In addition, nonuniformities in the excitation may lead to gain variations. Through numerical solutions it is found that even with nonuniform gain distribution in the transverse direction, the lower order optical modes as originally calculated represent the electromagnetic fields in the cavity rather accurately. The present work justifies earlier calculations of the number of oscillating off‐axis modes in lasers.

ISSN:0021-8979    

DOI:10.1063/1.1714358

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Because of the spatial variation of the electric fields and the finite size of the detector, the output current in a coherent optical detection process varies as a function of orientation. When two unfocused light beams impinge upon the detector, the output current is shown to be identical in form to the amplitude of the field generated at the origin of one of the sources by the other source when the detector is replaced by a reflector. If the effective aperture is increased by focusing the light beams with a single lens, then the directivity increases. However, if multiple apertures are used in order to maintain the images in the same position, the directivity is reduced. The detection of coangular beams, such as from the longitudinal modes of a laser, is relatively insensitive to angle of incidence.

ISSN:0021-8979    

DOI:10.1063/1.1714359

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The partial differential equation describing morphological changes of a surface of revolution due to capillarity‐induced surface diffusion has been derived under the assumption of isotropy of surface tension and surface self‐diffusion coefficient. A stable, convergent finite‐difference method has been developed for the general case of an arbitrary surface of revolution and solutions have been obtained for the specific problems of the blunting of field‐emission tips and the sintering of spheres. Spheroidization of cylindrical rods, as well as field‐emission tips with taper below a certain critical value, is predicted; for tapers above the critical value, steady‐state shapes are predicted and equations describing the blunting and recession of the tips are presented. If the sintering results for spheres are represented by a plot of logx/avs logt, it is found that the inverse slope varies from approximately 5.5 to approximately 6.5 for the range 0.05≤x/a≤0.3, in contrast with the constant value of 7 found by Kuczynski from an order‐of‐magnitude analysis. At higher values ofx/a, nincreases steadily and without bound.

ISSN:0021-8979    

DOI:10.1063/1.1714360

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

When a pulse of intense light from a laser passes through a plasma, a very small fraction of the light is scattered out of the beam by free electrons. Measurements of the intensity and spectral distribution of the scattered light can be related to the electron density and velocity distribution in the plasma. This paper presents a general discussion of the use of optical scattering as a plasma diagnostic technique. Applicability to various experimental situations is discussed, and considerations of interest in the design of diagnostic apparatus are presented.An apparatus has been constructed for the measurement of electron density in cold plasma. The apparatus is described in some detail. Typical results are given for densities as low as 1013electrons/cm3.

ISSN:0021-8979    

DOI:10.1063/1.1714361

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Transmission interference fringes from 2690 to 320 cm−1for InAs and from 1330 to 320 cm−1for CdTe have been analyzed with classical dispersion theory to obtain the room‐temperature dielectric constants. For InAs the dielectric constant between the band edge and the reststrahl &egr;∞and the static dielectric constant &egr;0are: &egr;∞= 11.8±0.1, &egr;0= 14.55±0.3; and for CdTe: &egr;∞= 7.05±0.05, &egr;0= 10.60±0.15. These values agree favorably with previously reported values. The absorption of InAs has been measured from 2500 cm−1, near the fundamental absorption edge, to 260 cm−1. Eight absorption peaks were observed between 444 and 269 cm−1which are attributed to multiphonon combinations with the following characteristic phonon frequencies: TO1= 222 cm−1, TO2= 214 cm−1, LO = 196 cm−1, and LA = 143 cm−1. The transmission of CdTe has been observed from 10 000 to 220 cm−1. From 10 000 to 450 cm−1the transmission is essentially constant at ∼60%. Below 400 cm−1only two previously reported transmission minima were observed.

ISSN:0021-8979    

DOI:10.1063/1.1714362

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The intensity of the 220 neutron reflection of a single crystal of yttrium iron garnet has been measured as a function of temperature from 4.2° up to 598°K. The information from this, when combined with measurements of the saturation magnetization, yields values for the sublattice magnetizationsMa(T) andMd(T) individually. As was found previously with lithium ferrite, the sublattice magnetizations are significantly higher at temperatures between 0.5Tcand 0.9Tc, whereTcis the Curie temperature, than those predicted by molecular field theory. It has been shown that the effect of a biquadratic term in the exchange interaction can be approximated by distorting the temperature scale such thatT/Tc= (T′/Tc)[1+&bgr;S2Ma(T′)Md(T′)/Ma(0)Md(0)], whereMa(T′) andMd(T′) are the sublattice magnetizations calculated at temperatureT′by molecular field methods,Sis the spin of the magnetic ions, and &bgr; is an adjustable parameter. If thea‐aandd‐dinteractions are neglected but the biquadratic correction is introduced with &bgr; = 0.04, the same value as in lithium ferrite, the fit with the experimental data is greatly improved. A maximum discrepancy of 5% between the observed and calculated magnetizations corresponds to a discrepancy of 1% in the sublattice magnetizations. This might be accounted for either by an improved approximation or by small values for thea‐aandd‐dinteractions.

ISSN:0021-8979    

DOI:10.1063/1.1714363

出版商:AIP    

年代:1965

数据来源: AIP