摘要:

It is demonstrated that equilibrium concentrations of surface vacancies on the principal planes of metal single crystals may exceed the concentrations of atoms in adsorbed positions. Surface vacancy concentrations on some of the higher index planes of gold are calculated to be of the order of 10−2or more at 1000°K. The interactions of mobile surface vacancies with steps are considered and contrasted with those of atoms diffusing on the surface. The possible influence of surface point defects on transport and growth mechanisms are discussed assuming that vacancy generation occurs mainly at kink sites on the free surface.

ISSN:0021-8979    

DOI:10.1063/1.1710080

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The hydrogen promotion technique for obtaining improved imaging condition for helium field‐ion microscopy of cobalt is described. The image quality is satisfactory for viewing stacking faults, twin boundaries, and phase boundaries between hcp cobalt and fcc cobalt in atomic dimensions. The stacking faults are bunched in hcp cobalt, the individual faults being separated on the average by ten atomic layers of the basal plane. Most of the faults jog every 20–30 Å. Many, parallel, thin, fcc plates were found in an hcp matrix. No effect of grain size on the transformation from the fcc to the hcp structure was observed. The ratio of the quantities of the two phases was affected by a small amount of impurity, and cobalt wire from one source had an fcc structure throughout the accessible temperature range and could not be made to transform to the hcp structure by various heat treatments.

ISSN:0021-8979    

DOI:10.1063/1.1710081

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A method for solving the heat equation for a particular set of discontinuous boundary conditions is presented. Calculated results are compared with a problem where the discontinuities have been averaged out. The method is of wider application than the present problem.

ISSN:0021-8979    

DOI:10.1063/1.1710082

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Measurements were made of Faraday rotation on ∼1‐&mgr;‐thick evaporated and recrystallized, polycrystalline InSb films. The experiments were carried out at room temperature using a microwave bridge circuit and a trimode turnstile as a polarimeter. The relative amplitudes and phases of the transmitted electric‐field components were determined with the film placed transversely across a circular waveguide section (TE11mode). Rotations of 30° to 40° were observed for a field of 2 kOe. The results are interpreted in terms of a theoretical model based on free‐carrier Faraday rotation including multiple reflections assuming plane‐wave propagation. The experimental data is in good quantitive agreement with the model forH<1.5 kOe and in qualitative agreement for higher fields.

ISSN:0021-8979    

DOI:10.1063/1.1710084

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The reflection of a dominant mode field at the junction of an air‐ferrite interface in a rectangular waveguide is investigated. A singular integral equation is derived for the interface electric field on the basis of the quasistatic approximation. The integral equation is solved by using a function‐theoretic technique. Closed‐form solutions valid for the entire range of medium parameters are developed assuming that the ferrite is entirely lossless. It is shown that these solutions can be made to satisfy the realness condition on the discontinuity reactance for the entire range of medium parameters. The above condition which can be proven directly on the basis of the Hermitian nature of the permeability tensor of the lossless ferrite was not satisfied by the previously published solution for a partial range of medium parameters. Finally, the modifications caused by the presence of the losses in the medium are discussed briefly.

ISSN:0021-8979    

DOI:10.1063/1.1710085

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A theoretical calculation is made from which the electrical conductivity or magnetic Reynolds number of a shock‐produced plasma flow can be derived. The results of the analysis predict the effects of the transient magnetic field induced by the interaction between the applied magnetic field and the plasma flow behind a shock wave. The applied magnetic field considered is transversal to the flow. Its intensity is either steady in time and increasing linearly in the flow direction or spatially uniform but increasing linearly with time.If the applied field extends to infinity, the intensity of the induced magnetic field is proportional to the magnetic Reynolds number and to the intensity of the applied magnetic field. With the aid of the present analysis the magnetic Reynolds number can be determined by comparison of the measured field and the calculated magnetic field. This method is applicable even if the magnetic Reynolds number is greater than unity. The effects of the finiteness of the applied field are considered.

ISSN:0021-8979    

DOI:10.1063/1.1710086

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The method of x‐ray‐diffraction topography, which is briefly described is applied to the study of magnetic domains in a single‐crystal sample of Tb3Fe5O12. Comparison is made with the same domain structure observed by transmitted polarized light and Bitter patterns, and a general interpretation of the diffraction topograph is suggested. Finally, the possible applications of the technique, particularly with respect to garnet materials, are briefly discussed.

ISSN:0021-8979    

DOI:10.1063/1.1710087

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The problem of electromagnetic scattering by homogeneous spheres with relative impedance equal to unity is considered. From the Mie series expression for the induced internal fields, the details of the condition responsible for producing a null in the backscattering cross section are deduced. The existence of this null is attributable solely to destructive interference, regardless of frequency, and is valid for either lossy or lossless media. The returned signal in the vicinity of the null is determined from numerical computation of the bistatic cross sections.

ISSN:0021-8979    

DOI:10.1063/1.1710088

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The magnetization vector in a conventional Ne´el wall between ferromagnetic domains is modified by a sinusoidal variation along the film thickness. Outside a small ``kernel'' region, the volume charge is cancelled by an appropriate choice of the second component of the magnetization vector (along the film thickness), while the surface charge vanishes everywhere along the wall. This configuration yields a wall energy which is somewhat smaller than the energy calculated by Brown and LaBonte as an absolute minimum of all one‐dimensional wall configurations, at least in the thickness of 103to 104Å in Permalloy. Since this is the thickness range in which the so called Bloch walls are usually observed experimentally, it seems that these walls do not have the one‐dimensional structure that is assigned to them, which can at most take place in bulk materials. For thickness of Permalloy much larger than 104Å, the energy of the new wall becomes larger than that of the conventional Bloch wall, and eventually it tends to infinity for an infinite film thickness.

ISSN:0021-8979    

DOI:10.1063/1.1710089

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

We have simulated the passage of heavy ions through a tungsten crystal in which the atoms are thermally displaced and the ions are subjected to a force which represents inelastic‐loss mechanisms. Semiempirical Born‐Mayer potential functions and inelastic‐loss parameters were obtained for the xenon‐tungsten and krypton‐tungsten systems. Only the xenon‐tungsten system was studied in detail. We find that below 500°K thermal displacement of the lattice atoms has little effect upon the collision dynamics for ions moving in the channel center. Energy losses to electronic processes during collisions are calculated, and the loss rates compared to the simulation loss rate parameter. Agreement is good. Simulated integral‐penetration curves agree quite well with the experimental results. A mechanism which attributes the strong temperature dependence of ranges to variations in the inelastic‐loss constants is presented and compared to experimental results.

ISSN:0021-8979    

DOI:10.1063/1.1710090

出版商:AIP    

年代:1967

数据来源: AIP