Search results for "eu"
showing 10 items of 80438 documents
Pressure-induced instability of the fergusonite phase of EuNbO4 studied by in situ Raman spectroscopy, x-ray diffraction, and photoluminescence spect…
2020
In this article, we present high-pressure experimental investigations on EuNbO4, an interesting technologically important material, using synchrotron based x-ray powder diffraction, Raman spectroscopy, and europium photoluminescence measurements up to 39.2, 31.6, and 32.4 GPa, respectively. All three techniques show the stability of the ambient monoclinic phase until 20 GPa. Beyond that, a pressure-induced structural phase transition takes place with the coexistence of two phases over a wide pressure range. The structure of the high-pressure phase has been determined as orthorhombic (space group: Imma) with a volume discontinuity of nearly 9% at the transition indicating the nature of trans…
The influence of AlN buffer over the polarity and the nucleation of self-organized GaN nanowires
2015
We experimentally investigate the influence of AlN buffer growth on the nucleation and the polarity of a self-organized assembly of GaN nanowires (NWs) grown on Si. Two complementary growth mechanisms for AlN buffer deposited on Si are demonstrated. Both emphasize the aggregation of Si on the AlN surface and the growth of large cubic crystallites, namely, AlN pedestals. Further growths of GaN NWs assembly reveal that the GaN 2D layer found at the bottom of the NW assembly is the result of the coalescence of Ga-polar pyramids, whereas AlN pedestals are observed as preferential but not exclusive NW nucleation sites. NWs are N-polar or exhibit inversion domains with a Ga-polar core/N-polar she…
Large Zero-Field Cooled Exchange-Bias in BulkMn2PtGa
2013
We report a large exchange-bias (EB) effect after zero-field cooling the new tetragonal Heusler compound Mn2PtGa from the paramagnetic state. The first-principle calculation and the magnetic measurements reveal that Mn2PtGa orders ferrimagnetically with some ferromagnetic (FM) inclusions. We show that ferrimagnetic (FI) ordering is essential to isothermally induce the exchange anisotropy needed for the zero-field cooled (ZFC) EB during the virgin magnetization process. The complex magnetic behavior at low temperatures is characterized by the coexistence of a field induced irreversible magnetic behavior and a spin-glass-like phase. The field induced irreversibility originates from an unusual…
Maximum Torque Per Ampere control algorithm for low saliency ratio interior permanent magnet synchronous motors
2017
This paper presents an investigation on the comparison between the Maximum Torque Per Ampere (MTPA) and the Field Orientation Control (FOC) algorithms for interior permanent magnet synchronous machines (IPMSMs). In particular, this study was carried out on a small-power IPMSM with low salience ratio. Both control algorithms have been implemented in the Matlab/Simulink environment, obtaining promising results.
Determination of fine magnetic structure of magnetic multilayer with quasi antiferromagnetic layer by using polarized neutron reflectivity analysis
2020
We carried out polarized neutron reflectivity (PNR) analysis to determine the fine magnetic structure of magnetic multilayers with quasi-antiferromagnetic (quasi-AFM) layers realized by 90-deg coupling using two Co90Fe10 layers, and quantitatively evaluated the magnetization of quasi-AFM layers. Two types of samples with different buffer layers, Ru buffer and a NiFeCr buffer, were investigated and the average angles between the respective magnetization of the two Co90Fe10 layers were estimated to be +/− 39 degrees and +/− 53 degrees. In addition, less roughness was found in the NiFeCr buffer sample resulting stronger 90-deg coupling. A perfect quasi-AFM is expected to be realized by a flat …
Nonlinear optical response of bulk ZnO crystals with different content of intrinsic defects
2018
Abstract The nonlinear optical (NLO) properties of native defect-rich ZnO single crystals were studied in details within the excitation of the continuous wave (CW) and pulsed laser radiation at 532 nm (2.33 eV). Analysis of the experimental data of optical elastic scattering, Fourier transform infrared (FTIR), near infrared–visible–ultraviolet (NIR–Vis–UV) spectra recorded in reflection and absorption modes, and data of photoluminescence (PL) spectroscopy confirmed the contribution of both intrinsic defects and their clusters, being determined before by neutron diffraction and XRD analysis. It was shown that the high sensitivity of the NLO diagnostics via self-action of a laser beam is due …
Neutron scattering and imaging: a tool for archaeological studies
2015
International audience; Neutron scattering and neutron imaging are powerful techniques for studying the structure of objects without damage, which is an essential prerequisite for investigations in Cultural Heritage domain, particularly in Archaeology. The deep penetration of neutrons in most materials allows for the study of relatively large objects. The contrast between similar materials, like metals in alloys, or that due to the presence of hydrogen atoms gives information about the internal structure of objects that have been modified or repaired in the past. Imaging and tomography give a 3-dimensional view of the whole object, permitting discrimination between different parts of the ob…
Preface for MMM 2016 focus issue
2017
International audience
High-frequency electrodeless lamps in argon–mercury mixtures
2005
In this paper, numerical and experimental investigations of high-frequency (HF) electrodeless lamps in argon–mercury mixtures are performed. The intensities of the mercury spectral lines having wavelengths λ = 404.66, 435.83, 546.07 nm (7 3S1–6 3P0,1,2) and the resonance line λ = 253.7 nm (6 3 P1–6 1S0) are measured at a wide range of mercury pressures, varying the HF generator current and argon filling pressure. A stationary self-consistent model of HF electrodeless discharge lamp is developed including kinetics of the excited mercury and argon atomic states. Based on the developed model, the radiation characteristics of the discharge plasma are calculated. Numerical simulation of the line…
Multi-application Based Fault-Tolerant Network-on-Chip Design for Mesh Topology Using Reconfigurable Architecture
2019
In this paper, we propose a two-step fault-tolerant approach to address the faults occurred in cores. In the first stage, a Particle Swarm Optimization (PSO) based approach has been proposed for the fault-tolerant mapping of multiple applications on to the mesh based reconfigurable architecture by introducing spare cores and a heuristic has been proposed for the reconfiguration in the second stage. The proposed approach has been experimented by taking several benchmark applications into consideration. Communication cost comparisons have been carried out by taking the failed cores as user input and the experimental results show that our approach could get improvements in terms of communicati…