摘要:

A model of recombination of carriers at the grain boundaries in polycrystalline silicon layers, taking into account the dynamics of capture and emission of carriers at the grain boundaries trapping states, is presented. Based on this model we investigate the electrical properties of polycrystalline silicon as a function of grain size under solar illumination. Comparison of our theoretical results with experimental results indicates that there is satisfactory agreement.

ISSN:0021-8979    

DOI:10.1063/1.337571

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The magnetization,geffand linewidth &Dgr;H∥and &Dgr;H⊥for liquid‐phase‐epitaxially grown thin films of EuxY3−xFe5−yGayO12(0.2≤x≤1.2;y=1.0) have been investigated in the temperature range 85–420 K. &Dgr;Hversus temperature curves show maxima which occur at about the same temperature as that observed in bulk single crystals of EuIG, but the width of the curves is narrower in the LPE films. The temperature and composition dependence ofgeffand &Dgr;Hhave been explained on the basis of the three sublattice model and a new relaxation mechanism based on anisotropic exchange.

ISSN:0021-8979    

DOI:10.1063/1.337572

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We analyze the magnetization distribution in the edge region of a magnetic thin film when a homogeneous magnetic field is applied. The present theory can analyze the general curling state in which surface and volume charges coexist in the film edge region. In addition, the theory can quantitatively show each energy as the energy parameters vary. We also analyze the magnetic field distribution and magnetic‐flux density distribution which are derived by the energy minimal magnetization distribution. The theory shows the good agreement with the experiment by the micro‐Kerr method when film thickness is small.

ISSN:0021-8979    

DOI:10.1063/1.337573

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Magnetic anisotropy of R2T14B (R=rare earth and T=transition metals such as Fe and Co) and partly substituted derivatives thereof are studied over a range of temperatures. The salient features are axial anisotropy for Y2Fe14B versus planar anisotropy for Y2Co14B. Only R with negative second‐order Stevens’ factor (such as Nd) will show axial anisotropy contributions near room temperature. However, even in this case nonaxial contributions compete at cryogenic temperature, leading to a spin reorientation for R=Nd and Ho withTRs=140 and 62 K, respectively, for the Fe‐based compounds. The symbol R is used to amplify the point that the spin reorientation is primarily triggered by an internal competition of R in question. The origin of this anisotropy competition is further illuminated by studies on partly R substituted materials, such as (Nd1−xRx)2Fe14B. Several contributions to the complex situation are considered including: (a) different site contributions (4f, 4g), (b) different order crystal‐field terms, such asV02,V22, andV04on 4fand 4g, (c) relative magnitude of exchange and crystal field, and (d) the trend for smaller R to preferentially occupy the 4fsite. Another type of spin reorientation is observed when R and T sublattice anisotropies compete. An example is Er2Fe14B withTR‐Ts=326 K. More complex mixed cases are either observed or predicted.

ISSN:0021-8979    

DOI:10.1063/1.337574

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

First‐order magnetization processes (FOMP) and spin reorientation phase transitions are known to occur in hexaferrites as well as in rare‐earth transition‐metal compounds. This complex phenomenology has been described using high‐order terms in the anisotropy energy expansion. In order to understand the microscopic origin of these high‐order anisotropy constants in hexaferrites we have made a detailed analysis of the magnetic properties of BaZn1.1Co0.9Fe16O27which shows, at the same temperature, easy cone anisotropy and a FOMP. We have found good agreement between the experimental data and the predictions of a simple two sublattice model which takes into account the effect of the competition between the exchange and the difference in the anisotropy of the sublattices. This strongly supports the hypothesis that such a competition and the subsequent noncollinear order are the origin of the observed large high‐order anisotropy constants in hexaferrites as in intermetallic compounds.

ISSN:0021-8979    

DOI:10.1063/1.337575

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Initial magnetization and demagnetization data are reported for three forms of rapidly solidified Nd‐Fe‐B permanent magnet materials: melt‐spun ribbons, hot‐pressed magnets, and die upset magnets. In all three materials, the results are consistent with domain‐wall pinning at Nd2Fe14B grain boundaries as the coercivity mechanism. Thermally demagnetized ribbons are comprised of single domain Nd2Fe14B grains, and both initial magnetization and demagnetization occur by depinning and wall motion. Domain walls move easily in die upset magnets until they become strongly pinned at grain edges. Complete magnetization requires an applied field greater than the coercive field. Hot‐pressed magnets show a mixture of ribbon and die upset behavior.

ISSN:0021-8979    

DOI:10.1063/1.337576

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Magnetic anisotropy dispersion in sputter‐deposited rare‐earth transition‐metal amorphous films is measured by the methods of Hall hysteresis loops and torque magnetometry. The inhomogeneity in the orientation of the easy axes of magnetization is found to be rather large; the mean inclination angle of the axes from film normal is 16.5° in a Gd–Tb–Fe film. Results show a clear correspondence between the anisotropy dispersion and Kerr rotation angle, and both depend on the bias voltage applied to the substrates during sputtering. Anisotropy dispersion is an important property for evaluating the amorphous magnetic films for magneto‐optical storage application.

ISSN:0021-8979    

DOI:10.1063/1.337577

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Photoluminescence spectra of single and coupled double wells were reanalyzed assuming a 62% partition of the band‐gap discontinuity to the conduction band and an energy‐dependent light‐hole effective mass. The photoluminescence peak positions of the single well are little affected when 62% instead of 85% is adopted for the partition value. The photoluminescence spectra of the coupled wells consist of a main peak and its satellites. Energy differences between the peak and its satellites are in good agreement with the calculated values when they are ascribed to transitions between doublet states in the conduction‐band well and doublet states in the valence‐band well, assuming a 62% partition and reasonable energy dependence of the light‐hole mass. This coupled double well offers a first evidence for the energy‐dependent light‐hole mass.

ISSN:0021-8979    

DOI:10.1063/1.337578

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The results of photoluminescence analysis of ion‐implanted and flash‐annealed CdTe are reported here. Bound exciton lines in the spectrum of the CdTe were used to study the annealing of implantation‐induced damage in the crystal. The intensity and width of these lines are a very good indicator of variations in lattice strain. Optimum flash annealing conditions were found to depend on both the energy and the dose of the implant. The photoluminescence indicates that flash annealing can provide complete annealing of the crystal damage following implantation. Implanting Cu or B ions into the lattice did not, however, lead to significant variations in the spectrum of the samples as compared to annealed, unimplanted samples. A comparison of flash and furnace annealing was made.

ISSN:0021-8979    

DOI:10.1063/1.337579

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The surface glow associated with Lucalox alumina insulator under high‐voltage dc and ac stress in bridged vacuum gaps was determined to be a continuum radiation with band limits from about 220 to 500 nm with a peak around 320 nm. A second peak with very low intensity was observed at longer wavelengths. Such surface luminescence from other materials (including different types of alumina) bridging the vacuum gap was either absent or too weak to be analyzed. There is ample evidence to support the view that the observed glow with Lucalox (99.9 wt. % Al2O3) is associated with electronic transitions between quantum‐mechanical states at defect sites (either interstitial atoms or vacancies) in the crystal structure of Al2O3. These defect sites are either theF+centers (one electron trapped at an anion vacancy, i.e., Al2+ion) or theFcenters (two electrons trapped at an anion vacancy, i.e., Al+ion). The results of this investigation indicate that the observed luminous front along an insulator surface in vacuum, prior to flashover, is not necessarily indicative of a streamer‐type discharge development in the gas phase, desorbed from the insulator surface. Such a luminous front is indicative of electronic transitions at defect sites located at or near the insulator surface.

ISSN:0021-8979    

DOI:10.1063/1.337580

出版商:AIP    

年代:1986

数据来源: AIP