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A flat band current-voltage-temperature and capacitance-voltage coupled method that helps evaluate band discontinuity in heterobarrier structures uses Fermi energy and barrier height at the flat band as parameters to eliminate errors in the evaluation. The method includes the effects of strain and nonparabolicity on band discontinuity. Application of this method to InGaAs/InAlAs heterointerfaces reveals a constant conduction-band offset ratio at 0.71.

We investigate the magnetic and magnetocaloric properties of the new Mn4-xFexGa2Sn compounds (x = 0, 0.1, 0.4, 0.6, and 0.8) from DC magnetization measurements. These phases crystallize in a lacunar form of the η-Fe2-xGe type of structure (P63/mmc). They present a second- order paramagnetic to ferromagnetic transition whose temperature increases upon increasing the Fe content from TC = 317 K for x = 0 up to TC = 411 K for x = 0.8. The alloys with x ≤ 0.4 further exhibit another transition at lower temperature associated with a spin reorientation. The maximal magnetization and magnetic entropy change are found almost constant throughout the series close to ~7.4 µB/f.u. and ~12 mJ cm-3 K-1 (for µ0ΔH = 2.4 T), respectively. The magnetocaloric properties of Mn4-xFexGa2Sn are compared with those of previously investigated materials with high- temperature magnetic transition and their potential interest for high-temperature magnetocaloric applications is briefly discussed. [ABSTRACT FROM AUTHOR]

We report on the kinetics of hydrogen absorption and desorption in magnetocaloric La(Fe,Si)13 materials based on experimental results and model calculations. In the model, the diffusion process is considered to take place dominantly in a hydriding or dehydriding reaction. An important parameter "characteristic absorption/desorption time" is introduced to predict the kinetics of hydriding/dehydriding reaction in a simple way. The application of the model on the La0.9Ce0.1Fe11.44Si1.56 compound gives coincident kinetic results with those determined from experiments. It indicates that the model provides an efficient guidance for measuring and comparing the kinetic property of the magnetocaloric La(Fe,Si)13Hy materials. [ABSTRACT FROM AUTHOR]

The in-plane aligned MnAs nanowires have been grown by molecular-beam epitaxy on GaAs(001) substrates at high growth temperature (≥450 °C). A discontinuous growth with break intervals (50 s’ interval per 10 s’ growth) was employed. The obtained nanowires were identified to be mainly type-B hexagonal MnAs. The influences of growth temperature and As4/Mn flux ratio on the nanowires’ morphology were investigated. Both high growth temperature and high As4/Mn flux ratio are necessary for the growth of uniaxially aligned MnAs nanowires with high aspect ratio. The magnetic anisotropy of the nanowires and their multimodal size distributions contribute to the large coercivity and special shape of the M-H loops along the magnetic easy axis, which is [1102]MnAs∥[110]GaAs. However, the longer growth time would lead to the both azimuthal alignments of the MnAs wires and the weakening of the magnetic anisotropy. [ABSTRACT FROM AUTHOR]

The magnetic and magnetocaloric properties of LaFe11.9-yCoySi1.1 compounds with y=0.8 and 0.9 have been investigated. The temperature dependence of magnetization data revealed that LaFe11.1Co0.8Si1.1 and LaFe11Co0.9Si1.1 exhibit a second-order magnetic transition near room temperature at 282 and 294 K, respectively. Under a magnetic field change of 5 T, the maximum values of isothermal entropy change -ΔS are found to be 15 and 13.5 J/kg K for y=0.8 and 0.9, respectively. The refrigerant capacity has been calculated to be 320 J/kg for y=0.8 and 266 J/kg for y=0.9 under a field change of 5 T. Direct measurements of the temperature change for LaFe11.9-yCoySi1.1 compounds around room temperature were also performed. Measurements of ΔT were performed in adiabatic conditions with practice-oriented method by using a specially developed test bench. For both materials, the normalized temperature change was found to be about 1 K/T at their Curie temperatures. [ABSTRACT FROM AUTHOR]

Investigates the surface electric field of silicon delta-doped GaAs grown by molecular beam epitaxy at a low substrate temperature using photoreflectance spectroscopy. Observations on Franz-Keldysh oscillations in the reflectance spectra; Explanation for the evolution of photoreflectance spectra; Use of photoreflectance in the study of semiconductors.

Focuses on a study which characterized the redistribution of arsenic precipitates in silicon δ-doped gallium arsenide through x-ray diffractometry and transmission electron microscopy. Experimental details; Results and discussion; Conclusion.

In this paper, we report on the magnetic properties and magnetocaloric effect (MCE) in NaZn13-type LaFe11.2Co0.7Si1.1Cx (x=0.1 and 0.3) close to room temperature. The Landau theory as well as the temperature dependence of magnetization data revealed that LaFe11.2Co0.7Si1.1C0.1 and LaFe11.2Co0.7Si1.1C0.3 exhibit a second-order magnetic transition near their Curie temperature. We have calculated the magnetocaloric effect both in terms of isothermal entropy change and adiabatic temperature change using the magnetization and the direct measurements. Under an external field change from 0 to 5 T, -ΔS is 14.5 J/kg K (TC=290 K) and 8 J/kg K (TC=310 K) for x=0.1 and 0.3, respectively. The calculated refrigerant capacity for a field change in 0-5 T is about 305 and 286 J/kg K, for LaFe11.2Co0.7Si1.1C0.1 and LaFe11.2Co0.7Si1.1C0.3respectively, which is larger than that of some magnetocaloric materials with a first-order phase transition (Gd5Ge2Si2). ΔTad decreases with increasing C content. It was found to be about 1.5 for x=0.1 and 1.2 for x=0.3 under 1.48 T. [ABSTRACT FROM AUTHOR]

Results on both field driven and current induced domain wall motion in Co/Cu/Ni80Fe20 trilayered half-ring in-series wires with different linewidths were presented. The switching behavior depends linearly on the linewidth of Co/Cu/Ni80Fe20 trilayered half-ring structures. A larger bias field (Hb) applied to the samples results in a smaller critical current needed to reverse magnetization. The critical current density was observed to be 3×107 A/cm2 for Ni80Fe20 and 2×108 A/cm2 for Co at zero field. The results of the numbers of giant magnetoresistance jump (digital) versus external magnetic field and current densities (analog) of this design have potential utility as an analog-digital converter. [ABSTRACT FROM AUTHOR]

Nickel/lead multilayered nanowires were prepared using standard three-electrode electrodeposition into anodic aluminum oxide porous templates. The diameters of the nanowires ranged from 50 to 200 nm. By means of electric and magnetic measurements, we found that the superconducting transition temperature, Tc, of the Pb layer persisted down to the smallest diameter without any noticeable dimensional effect. Tc was affected by the relative orientation of magnetizations in neighboring Ni layers. When the superconducting layers were driven normal under a large magnetic field, unusual resistance increase was observed with decreasing temperature, which was consistent with the Kondo effect. [ABSTRACT FROM AUTHOR]

Structural and magnetic properties of Ga0.93Mn0.07As layers grown on (001) and (311)A GaAs substrates by molecular-bean epitaxy are investigated. The as-grown (001) and (311)A Ga0.93Mn0.07As layers exhibit the same Curie temperature (TC) of 80 K. However, upon annealing, the TC’s of the (001) and (311)A Ga0.93Mn0.07As layers are enhanced by 80 and 60 K, respectively. X-ray diffraction studies reveal that the AsGa defects cannot be removed by low-temperature annealing, and a higher concentration of AsGa defects exist in the (311)A layers than in the (100) reference layers. The less enhancement in TC by annealing for the (311)A Ga0.93Mn0.07As layer can be ascribed to the larger amount of AsGa defects in the material. [ABSTRACT FROM AUTHOR]

A spin transistor consisting of a metallic pseudo-spin-valve emitter, a copper base, and a p-n junction collector was prepared on a Si(100) wafer. This spin transistor can provide high magnetocurrent output, high magnetocurrent variation, and high transfer ratio. The common collector configuration with an emitter bias of 5.12 V at 77 K gives a large magnetocurrent variation of more than 95.5 μA in the collector, and the change is more than 3400% with a transfer ratio of 2.59310-3. At room temperature, these changes go down to 98.3 μA and 55.3%, respectively, and the transfer ratio rises to 5.98310-3. The high performance of this spin-valve transistor is due to the use of a p-n junction as an energy barrier to select spin electrons. [ABSTRACT FROM AUTHOR]