Search results for "CELLA"

2019

We systematically study the pump-wavelength dependence of terahertz pulse generation in thin-film spintronic THz emitters composed of a ferromagnetic CoFeB layer between adjacent nonmagnetic W and Pt layers. We find that the efficiency of THz generation is essentially flat for excitation by 150 fs pulses with center wavelengths ranging from 900 to 1500 nm, demonstrating that the spin current does not depend strongly on the pump photon energy. We show that the inclusion of dielectric overlayers of TiO2 and SiO2, designed for a particular excitation wavelength, can enhance the terahertz emission by a factor of up to two in field.

Enhancing domain wall velocity through interface intermixing in W-CoFeB-MgO films with perpendicular anisotropy

2019

We study the influence of He+ irradiation induced interface intermixing on magnetic domain wall (DW) dynamics in W-CoFeB (0.6 nm)-MgO ultrathin films, which exhibit high perpendicular magnetic anisotropy and large Dzyaloshinskii-Moriya interaction (DMI) values. Whereas the pristine films exhibit strong DW pinning, we observe a large increase in the DW velocity in the creep regime upon He+ irradiation, which is attributed to the reduction of pinning centers induced by interface intermixing. Asymmetric in-plane field-driven domain expansion experiments show that the DMI value is slightly reduced upon irradiation, and a direct relationship between DMI and interface anisotropy is demonstrated. …

Corrosion of Welded Metal Structures of Mining Equipment

2018

Mining equipment made of welded metal structures is strongly affected by the corrosion phenomenon due to the working conditions. Initial research has shown that the corrosion phenomenon is most pronounced in the area of cross-welded joints and welded T-shaped joints. In the researches, there was made a chemical analysis of the welded construction material used respectively of the new material and it was observed a reduction in carbon concentration in the material used, but also a substantial increase in the sulfur concentration compared to the new material. The pronounced corrosion of the metallic structure is influenced by the chemical composition change because the sulfur is a grafitizin…

Reactive Sintering of molybdenum disilicide by Spark Plasma Sintering from mechanically activated powder mixtures: Processing parameters and properti…

2008

Abstract Dense molybdenum disilicide with a nano-organized microstructure was synthesized by mechanical activation, by producing nanostructured agglomerates of a 1:2 mixture of Mo and Si, followed by the synthesis/consolidation in one step using SPS technology. In order to synthesize a dense molybdenum disilicide with a perfectly controlled microstructure, an investigation of the influence of Spark Plasma Sintering processing parameters (temperature, heating rate, mechanical pressure and holding time) on the chemical composition and the microstructure characteristics has been performed. The present work shows also that the so-obtained materials present better oxidation resistance in compari…

Nucleation of GaN nanowires grown by plasma-assisted molecular beam epitaxy: The effect of temperature

2011

Abstract The growth of GaN nanowires by means of plasma assisted molecular beam epitaxy directly on Si(1 1 1) has been investigated as a function of temperature. Statistical analysis of scanning electron microscopy pictures taken for different growth temperatures has revealed that density, diameter, length and length dispersion of nanowires were strongly dependent on temperature. Length dispersion, in particular, was found to be significant at high temperature. These features have been assigned to the different duration of the nucleation process with temperature, namely to the dependence with temperature of the time necessary for the size increase of the three-dimensional precursors up to a…

Band gap of corundumlike α−Ga2O3 determined by absorption and ellipsometry

2017

The electronic structure near the band gap of the corundumlike $\ensuremath{\alpha}$ phase of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ has been investigated by means of optical absorption and spectroscopic ellipsometry measurements in the ultraviolet (UV) range (400--190 nm). The absorption coefficient in the UV region and the imaginary part of the dielectric function exhibit two prominent absorption thresholds with wide but well-defined structures at 5.6 and 6.3 eV which have been ascribed to allowed direct transitions from crystal-field split valence bands to the conduction band. Excitonic effects with large Gaussian broadening are taken into account through the Elliott-Toyozawa model, which y…

The role of seed electrons on the plasma breakdown and preglow of electron cyclotron resonance ion source

2009

The 14 GHz Electron Cyclotron Resonance Ion Source at University of Jyväskylä, Department of Physics (JYFL) has been operated in pulsed mode in order to study the plasma breakdown and preglow effect. It was observed that the plasma breakdown time and preglow characteristics are affected by seed electrons provided by a continuous low power microwave signal at secondary frequency. Sustaining low density plasma during the off-period of high power microwave pulses at the primary frequency shifts the charge state distribution of the preglow transient toward higher charge states. This could be exploited for applications requiring fast and efficient ionization of radioactive elements as proposed f…

Cold gas dynamic spray technology: A comprehensive review of processing conditions for various technological developments till to date

2018

Abstract Today, cold gas dynamic spray (CGDS) technology has thrived with considerable capabilities for manufacturing various technological depositions. The deposition conditions have been developed through many years and that have led to produce ample experimental data which is available in the literature. But, recent research and development activities also reveal innovative findings regarding various deposition conditions. This paper contains a review of experimental deposition procedures for the cold spray additive manufacturing. Details of processing conditions are reported and classified into various categories of baseline working conditions, specific processing including deposition o…

Crystalline phase detection in glass ceramics by EPR spectroscopy

2018

The advances of EPR spectroscopy for the detection of activators as well as determining their local structure in the crystalline phase of glass ceramics is considered. The feasibility of d-element (Mn2+, Cu2+) and f-element (Gd3+, Eu2+) ion probes for the investigation of glass ceramics is discussed. In the case of Mn2+, the information is obtained from the EPR spectrum superhyperfine structure, for Gd3+ and Eu2+ probes – from the EPR spectrum fine structure, whereas for Cu2+ ions the changes in the EPR spectrum shape could be useful. The examples of EPR spectra of the above-mentioned probes in oxyfluoride glass ceramics are illustrated. ----/ / /---- This is the preprint version of the fol…

Hydrodynamic Modeling of Transport and Noise Phenomena in Bipolar Two-Terminal Silicon Structures

1998

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