摘要:

The continuous magnetization of a 180° one‐dimensional interdomain wall in a ferromagnetic thin film is replaced by a discrete distribution for which the magnetostatic energy can be calculated rigorously. The general functional form of the direction of magnetization within the wall is not restricted by this replacement, and minimization of the total energy with the aid of a digital computer yields both the equilibrium wall structure and its corresponding energy. It is found that only Bloch and Ne´el types of one‐dimensional walls result. The magnetization distribution of a typical Bloch wall is shown, and the Bloch wall energy and wall thickness are calculated as functions of film thickness and compared with values from the literature. Finally, some detail of the Ne´el wall structure is presented, and it is shown that the transition from one‐dimensional Bloch to Ne´el walls should occur at much larger film thickness than has been reported previously.

ISSN:0021-8979    

DOI:10.1063/1.1714314

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A decrease in the cathodoluminescence produced in GaAs by a scanning electron probe has been observed when the probe is close to ap‐njunction. The decreased intensity is shown to result from the drift of excess carriers across the junction. Measurements of the short‐circuit current of the diode confirm this interpretation and provide a means of estimating minority carrier diffusion lengths.

ISSN:0021-8979    

DOI:10.1063/1.1714315

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A method has been developed for determining electron drift velocities from measured current‐voltage characteristics of gas‐filled cylindrical diodes. Experimental data, taken in diodes filled with helium, nitrogen, and argon, are presented to illustrate the utility of the method.

ISSN:0021-8979    

DOI:10.1063/1.1714316

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The transition between Ne´el and Bloch walls is shown to be gradual rather than abrupt, resulting in a wall with Ne´el and Bloch components superposed. For films thick enough so that such a transition can occur, the wall is a pure Ne´el wall if &phgr;f, the acute angle between the wall normal in the plane of the film and the magnetization at the edge of the wall (half the angle between the magnetization vectors in the two domains separated by the wall) is less than a critical value. For &phgr;flarger than that critical value but less than &pgr;/2, the wall contains both Ne´el and Bloch components. When &phgr;fis &pgr;/2, i.e., a 180° wall, the wall is of the pure Bloch type; however, this situation is often unstable, resulting in a transition wall with the Ne´el component reversing periodically in distance along the wall in a crosstie‐like structure. These conclusions are supported by Lorentz micrographs.

ISSN:0021-8979    

DOI:10.1063/1.1714317

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

We have obtained exactly the excess dissipation due to a small spherical inclusion in a semiconductor, using the same model of the semiconductor which was investigated in previous papers of this series, and the ``four moment approximation'' to the electron‐distribution function. We have also calculated the high‐field limit of the transverse magnetoresistance for a dilute sprinkling of spherical inclusions, which is proportional to the high‐field limit of the excess dissipation, and varies as|H|asH→∞, whereHis the magnetic field. Previously, Herring obtained approximately the excess dissipation of a cylindrical inclusion with axis parallel to the magnetic field and made plausible a high‐field transverse magnetoresistance which varies as|H|/ln|H|asH→∞. In the case of spherical inclusion, we can investigate in detail perturbations produced by the external specimen boundaries, and we suggest that analogous results hold for a cylindrical inclusion.

ISSN:0021-8979    

DOI:10.1063/1.1714318

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A simplified theory of the effect of strain on the acceptor states in GaAs is used to account for observations made on electroluminescent diodes, the optical transition being between the conduction band and the acceptor states. The acceptor states are described as having a hydrogenic envelope inkspace, and as being constituted primarily of states of the heavy mass band. The calculated changes in intensity and the line splitting are in fair agreement with experiment, but no explanation of the observed line shift has yet been found.

ISSN:0021-8979    

DOI:10.1063/1.1714319

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

In previous treatments of metal‐semiconductor contact barrier height measurements by the differential capacitance method it has been generally assumed that there exists an Ohmic reference contact to the semiconductor. In this paper, the method is extended to those cases where an Ohmic contact to the semiconductor isnotavailable. It is shown that under certain conditions, barrier heights may be determined using only barrier reference contacts. It is also shown that although only two contacts are necessary, a third contact may be advantageously employed to simplify the measurement technique. If four contacts are available, a further simplification may be achieved.Experimental results on Au&sngbnd;CdS contacts are used to verify the theory for the case of two symmetrical barrier contacts.

ISSN:0021-8979    

DOI:10.1063/1.1714320

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

It is shown in this paper that (1) the geometrical window of the instrument is a function of the alignment of the crystals, the beam, and the rotation axes as well as the vertical divergence, (2) even for the case of perfect spectrometer alignment, errors are introduced into the measurement of the spectral parameters because of the presence of a finite vertical divergence in the x‐ray beam, and (3) improper beam and crystal alignment cause inaccuracies in the measurement of spectral parameters, e.g., wavelength position, linewidth, line shape, and asymmetry.Calculations which predict the effects of vertical divergence and of beam and crystal misalignment on the geometrical window and also on the wavelength position, line shape, linewidth, and line asymmetry of the (1,+1) and (1,−1) curves are made for the case of CuK&agr; radiation reflected from calcite crystals. In particular, it is shown that the error in the measurement of the Bragg angle, i.e., wavelength, is 61/2times more sensitive to misalignment of the central ray of the x‐ray beam than it is to total vertical divergence.

ISSN:0021-8979    

DOI:10.1063/1.1714321

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Conditions for and methods of aligning a two‐crystal spectrometer are discussed. These include the alignment of rotation axes, crystals, and x‐ray beam. The results of a new nondispersive crystal alignment procedure are compared in detail with theory for a typical case of CuK&agr; radiation and calcite crystals. This method is contrasted with other procedures which lead only to pseudo‐alignments.It is shown that x‐ray methods which are sensitive to vertical divergence do not lead to crystal alignment unless the beam is already perfectly aligned. It is concluded that the x‐ray beam can be aligned onlyafterthe crystals have been aligned.

ISSN:0021-8979    

DOI:10.1063/1.1714322

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

By applying high electric fields to triglycine sulfate at temperatures close to the Curie point, switching times of the order of nanoseconds were observed. It was assumed, from previous studies, that at these high fields all domain nuclei form almost at the same time and grow together through the thickness of the specimen. In this case the transit time for the domain nuclei is almost equal to the switching time and the experimental results show that the domain velocities observed in the faster switching times were supersonic. A sudden increase in wall mobility occurred at the transition from subsonic to supersonic velocities. Both the supersonic and the subsonic mobilities are thickness‐dependent. Models to explain these effects in a qualitative way are provided.

ISSN:0021-8979    

DOI:10.1063/1.1714323

出版商:AIP    

年代:1965

数据来源: AIP