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31.
Structure, electric and dielectric studies of indium-substituted magnesium copper manganese ferrites
M. Kaiser 《Physica B: Condensed Matter》2011,406(4):899-905
The structure, electric and dielectric properties of In-substituted Mg-Cu-Mn ferrites having the general formula of Mg0.9Cu0.1Mn0.1InxFe1.9−xO4 with 0.0≤x≤0.4 have been studied. X-ray diffraction (XRD) patterns of the samples indicated the formation of single-phase cubic spinel structure up to 0.2 and mixed phase (cubic and tetragonal phase) for samples x≥0.3. The relation of conductivity with temperature revealed a semiconductor to semimetal behavior as In+3 concentration increases. Variation in the universal exponent s with temperature indicates the presence of two hopping conduction mechanisms: the correlated barrier hopping (CHB) at low In+3 content x≤0.1 and small-polaron (SP) hopping at In+3 content x≥0.2. The variation in dielectric permittivity (ε′, ε″) with temperature at different frequencies shows a normal behavior for the studied compounds, while the variation in dielectric loss tangent with frequency at different temperatures shows abnormal behavior with more than relaxation peak. The conduction mechanism used in the present study has been discussed in the light of electron exchange between Fe3+ and Fe2+ ions and hole hopping between Mn2+ and Mn3+ ions at the octahedral B-sites. 相似文献
32.
33.
Th. Stammler T. Grund A.B. Kaiser J. Major A. Röck R. Scheuermann L. Schimmele A. Seeger 《Hyperfine Interactions》1997,104(1-4):331-336
High‐pressure μSR experiments on ferromagnetic nickel and \alpha‐iron and antiferromagnetic chromium are reported. In Ni above
260 K BFermi was found to be proportional to the saturation magnetization, whereas at lower temperatures it is temperature independent
apart from a small anomaly below 30 K which is presumably caused by a magnetoelastic interaction. There was no evidence for
an occupation of metastable sites by the μ+ below the Curie temperature. By contrast, in \alpha‐Fe the temperature dependence of \curpartialBμ/\curpartialp shows a structure which might be attributed to the occupation of excited muon states at elevated temperatures.
High‐pressure zero‐field experiments on Cr performed in the temperature regime between 4.5 K and 8 K revealed a pressure dependence
of Bμ as large as \curpartialBμ/\curpartialp=-(89.15\pm 0.06)\times 10-12 T/Pa. In terms of volume dependence a very large negative Grüneisen parameter \gamma =-27 was obtained.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
34.
Scales in nuclear matter: Chiral dynamics with pion nucleon form factors<Superscript>⋆</Superscript>
N. Kaiser M. Mühlbauer W. Weise 《The European Physical Journal A - Hadrons and Nuclei》2007,31(1):53-60
A systematic calculation of nuclear matter is performed which includes the long-range correlations between nucleons arising
from one- and two-pion exchange. Three-body effects from 2π exchange with excitations of virtual Δ(1232)-isobars are also
taken into account in our diagrammatic calculation of the energy per particle ˉ(k
f). In order to eliminate possible high-momentum components from the interactions we introduce at each pion-baryon vertex a
form factor of monopole type. The empirical nuclear matter saturation point, ρ0 ≃ 0.16fm^-3, ˉ0 ≃ - 16MeV, is well reproduced with a monopole mass of Λ ≃ 4πf
π ≃ 1.16GeV. As in the recent approach based on the universal low-momentum NN potential V
low-k, the inclusion of three-body effects is crucial in order to achieve saturation of nuclear matter. We demonstrate that the
dependence of the pion exchange contributions to ˉ(k
f) on the “resolution” scale Λ can be compensated over a wide range of Λ by counterterms with two “running” contact couplings.
As a further application we study the in-medium chiral condensate 〈ˉq〉(ρ) beyond the linear density approximation. For ρ ⩽ 1.5ρ0 we find small corrections from the derivative dˉ(k
f)/dm
π, which are stable against variations of the monopole regulator mass Λ. 相似文献
35.
Andriy Romanyuk Viktor Melnik Yaroslav Olikh Johannes Biskupek Ute Kaiser Martin Feneberg Klaus Thonke Peter Oelhafen 《Journal of luminescence》2010,130(1):87-91
Silicon clusters embedded in a silicon dioxide matrix were prepared by ultrasound-assisted implantation resulting in a modified concentration of suboxide states as revealed by high-resolution photoelectron spectroscopy. It is suggested that ultrasound treatment results in formation of different interface structure between silicon cluster and silicon dioxide matrix which is characterized by a distinctly reduced concentration of the suboxide states. It is observed that photoluminescence properties are strongly correlated with the concentration of the suboxide states thereby providing an evidence that besides a quantum confinement effect a closer look at the chemical composition of the nc-Si/SiO2 system is important. 相似文献
36.
The Soreq Applied Research Accelerator Facility (SARAF): Overview,research programs and future plans
Israel Mardor Ofer Aviv Marilena Avrigeanu Dan Berkovits Adi Dahan Timo Dickel Ilan Eliyahu Moshe Gai Inbal Gavish-Segev Shlomi Halfon Michael Hass Tsviki Hirsh Boaz Kaiser Daniel Kijel Arik Kreisel Yonatan Mishnayot Ish Mukul Ben Ohayon Michael Paul Amichay Perry Hitesh Rahangdale Jacob Rodnizki Guy Ron Revital Sasson-Zukran Asher Shor Ido Silverman Moshe Tessler Sergey Vaintraub Leo Weissman 《The European Physical Journal A - Hadrons and Nuclei》2018,54(5):91
37.
The compound 2,10-dibromo-3-chloro-8-hydroxy-β-chamigrene was analysed in detail by NMR Spectroscopy. the complete assignment of the signals in the 1H and 13C NMR spectra and the determination of the relative configurations were achieved by 2D NMR techniques, AM1 data and 1H spectrum simulation. Comparisons of the results with related spiro chamigrene systems are also presented. 相似文献
38.
A. S. Prokhorov V. B. Anzin D. A. Vitukhnovskiĭ E. S. Zhukova I. E. Spektor B. P. Gorshunov S. Vongtragool M. B. S. Hesselberth J. Aarts G. J. Nieuwenhuys M. Dumm D. Faltermeier S. Kaiser S. Yasin M. Dressel N. Drichko 《Journal of Experimental and Theoretical Physics》2006,103(6):887-896
The electrodynamic response of spin glasses (in the form of thin AuFe films) in the terahertz frequency range has been studied using backward-wave oscillator (BWO) spectroscopy (10–40 cm?1) and optical ellipsometry (5000–33000 cm?1) techniques at temperatures from 5 to 295 K. The room-temperature dynamic conductivity spectra of AuFe films are typical of metals and can be described within the framework of the Drude theory of conduction by free charge carriers. Changes in the microscopic parameters of charge carriers in AuFe films with increasing iron content, which are related to additional scattering of carriers on the impurity magnetic moments, have been studied on the quantitative level, including the carrier relaxation frequency and characteristic time, plasma frequency, and conductivity. It is established that the spin-glass phase at a temperature of ~5 K exhibits dispersion of the conductivity in the frequency range 10–40 cm?1, which can be related to the appearance of a mobility gap in the subsystem of free electrons involved in the RKKY interaction between magnetic centers (Fe atoms). 相似文献
39.
M. Sendova B. Kaiser M. Scalera V. Zhelyaskov 《Journal of Raman spectroscopy : JRS》2010,41(4):469-472
Micro‐Raman temperature study and X‐ray fluorescence (XRF) spectroscopy were used for characterization of the blue glaze on Saint John the Baptist—majolica terracotta relief attributed to Andrea Della Robbia and Saint John the Baptist with Cross—majolica terracotta statue attributed to Giovanni Della Robbia. Both objects are on permanent exhibition in the John and Mable Ringling Museum of Art in Sarasota, FL. This study proves that the detection of the 548 cm−1 Raman band alone cannot serve as evidence for presence of lazurite crystallites in the pigment in the glaze. It was established that the famous Della Robbia blue is due to the combined effect of Co Ni Cu Zn atoms and S3− ions embedded in a lead silicate matrix. It is proposed that the Della Robbia family used Co‐containing sulfide ores as a source for manufacturing their blue pigments. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
40.
Rongji Liu Kecheng Cao Adam H. Clark Peilong Lu Montaha Anjass Johannes Biskupek Ute Kaiser Guangjin Zhang Carsten Streb 《Chemical science》2020,11(4):1043
The top-down fabrication of catalytically active molecular metal oxide anions, or polyoxometalates, is virtually unexplored, although these materials offer unique possibilities, for catalysis, energy conversion and storage. Here, we report a novel top-down route, which enables the scalable synthesis and deposition of sub-nanometer molybdenum-oxo clusters on electrically conductive mesoporous carbon. The new approach uses a unique redox-cycling process to convert crystalline MoIVO2 particles into sub-nanometer molecular molybdenum-oxo clusters with a nuclearity of ∼1–20. The resulting molybdenum-oxo cluster/carbon composite shows outstanding, stable electrocatalytic performance for the oxygen reduction reaction with catalyst characteristics comparable to those of commercial Pt/C. This new material design could give access to a new class of highly reactive polyoxometalate-like metal oxo clusters as high-performance, earth abundant (electro-)catalysts.The top-down synthesis and deposition of polyoxometalate-like clusters on porous carbon is reported together with the high electrocatalytic oxygen reduction reactivity of the composite. 相似文献