Search results for "Weiss"
showing 10 items of 47 documents
Magnetization and61Ni Mössbauer effect study of the ternary arsenide CrNiAs
2008
The results of x-ray diffraction, dc magnetization, and 61Ni M?ssbauer spectroscopy studies of the ternary arsenide CrNiAs are reported. This compound crystallizes in the orthorhombic Fe2P-type structure (space group ) with the lattice parameters a = 6.1128(2)?? and c = 3.6585(1)??. CrNiAs is a mean-field ferromagnet with Curie temperature TC = 171.9(1)?K and the critical exponents ? = 0.514(18), ? = 1.010(16), and ? = 2.922(10). The temperature dependence of the magnetic susceptibility above TC follows the modified Curie?Weiss law with a paramagnetic Curie temperature of 176.0(3)?K and effective magnetic moment per transition metal atom of 2.42(1)??B. The magnetic moment per formula unit a…
Grain-size-induced relaxor properties in nanocrystalline perovskite films
2004
Thin films of ${\mathrm{Pb}}_{0.76}{\mathrm{Ca}}_{0.24}{\mathrm{TiO}}_{3}$ (PTC), which is a classical ferroelectric as a bulk material and of the relaxor material $\mathrm{Pb}({\mathrm{Sc}}_{0.5}{\mathrm{Nb}}_{0.5}){\mathrm{O}}_{3}$, have been produced to find out whether nanocrystalline ferroelectric films show a grain-size-induced relaxor behavior. Amorphous films were deposited onto a $\mathrm{Ti}∕\mathrm{Pt}$ coated silicon (100) wafer by reactive $\text{rf}$ sputtering. Different grain sizes were prepared by a controlled annealing process and they were determined by profile analysis of x-ray diffraction spectra. Temperature dependent Raman spectroscopy was used to look for phase trans…
Itinerant Electron Metamagnetism in η-Carbide-Type Compound Co3Mo3C
2010
We report the magnetic properties of the cobalt molybdenum η-carbide-type compounds Co 3 Mo 3 C and Co 3 Mo 3 N. The magnetic susceptibility χ of Co 3 Mo 3 C shows a Curie–Weiss temperature dependence at high temperatures and a broad maximum at around 100 K, whereas that of Co 3 Mo 3 N shows a nearly temperature-independent enhanced Pauli paramagnetic behavior. The absence of a magnetic long-range order was confirmed by the nuclear magnetic resonance technique in both the compounds. As expected from the broad maximum of χ, we observed an itinerant electron metamagnetic transition at around 37 T in Co 3 Mo 3 C.
Geometric, electronic, and magnetic structure ofCo2FeSi: Curie temperature and magnetic moment measurements and calculations
2005
In this work a simple concept was used for a systematic search for materials with high spin polarization. It is based on two semiempirical models. First, the Slater-Pauling rule was used for estimation of the magnetic moment. This model is well supported by electronic structure calculations. The second model was found particularly for ${\mathrm{Co}}_{2}$ based Heusler compounds when comparing their magnetic properties. It turned out that these compounds exhibit seemingly a linear dependence of the Curie temperature as function of the magnetic moment. Stimulated by these models, ${\mathrm{Co}}_{2}\mathrm{FeSi}$ was revisited. The compound was investigated in detail concerning its geometrical…
Astronomical calibration of the Valanginian and the Hauterivian stages (lower cretaceous) : paleoclimatic and paleooceanographic implications
2013
Orbital floating time scales are proposed for the Valanginian Stage and part of the Hauterivian Stage (Early Cretaceous). These are based on the identification of the eccentricity cycles from spectral analyses performed on high-resolution climatic proxies measured on hemipelagic marl-limestone alternations. Five reference sections were analysed in the Vocontian Basin (SE France), spanning the entire Valanginian. A duration of 5,08 myr is proposed for the Valanginian Stage from the identification of the 405-kyr eccentricity cycle. The time frame proposed, combined with available radiometric ages, shows that the mid-Valanginian 13C positive excursion (namely the Weissert Event) occurs prior …
Selection of amine-oxidizing dairy lactic acid bacteria and identification of the enzyme and gene involved in the decrease of biogenic amines
2016
ABSTRACT Accumulation of biogenic amines (BAs) in cheese and other foods is a matter of public health concern. The aim of this study was to identify the enzyme activities responsible for BA degradation in lactic acid bacteria which were previously isolated from traditional Sicilian and Apulian cheeses. The selected strains would control the concentration of BAs during cheese manufacture. First, 431 isolates not showing genes encoding the decarboxylases responsible for BA formation were selected using PCR-based methods. Ninety-four out of the 431 isolates degraded BAs (2-phenylethylamine, cadaverine, histamine, putrescine, spermine, spermidine, tyramine, or tryptamine) during cultivation on …
Molecular analysis of the dominant lactic acid bacteria of chickpea liquid starters and doughs and propagation of chickpea sourdoughs with selected W…
2020
Abstract Fermented chickpea liquid is used as a leavening agent in chickpea bread production. In the present study, traditional chickpea liquid starter and dough samples were collected from bakeries in Turkey and microbiologically investigated. Culture-independent analysis for microbiota diversity, performed by MiSeq Illumina, identified Clostridium perfringens as major group in all samples, while Weissella spp. Dominated LAB community. A culture-dependent methodology was applied and 141 isolates were confirmed to be members of the LAB group based on 16s rRNA gene sequence analysis. In particular, 11 different LAB species were identified confirming the high frequency of isolation of weissel…
Background discrimination capabilities of a heat and ionization germanium cryogenic detector
2001
The discrimination capabilities of a 70 g heat and ionization Ge bolometer are studied. This first prototype has been used by the EDELWEISS Dark Matter experiment, installed in the Laboratoire Souterrain de Modane, for direct detection of WIMPs. Gamma and neutron calibrations demonstrate that this type of detector is able to reject more than 99.6% of the background while retaining 95% of the signal, provided that the background events distribution is not biased towards the surface of the Ge crystal. However, the 1.17 kg.day of data taken in a relatively important radioactive environment show an extra population slightly overlapping the signal. This background is likely due to interactions o…
Effect of cobalt doping on the dielectric response of $B_{0.95}Pb_{0.05}TiO_3$ ceramics
2013
Dielectric response of Ba 0.95 Pb 0.05 TiO 3 ceramics doped with 0.1 and 1 wt.% of Co 2 O 3 , synthesized by conven- tional high-temperature method, wa s studied in wide temperature and frequency range. The temperature dependences of the real and the imaginary parts of dielectric permittivity of the ceramics were compared with those of BaTiO 3 and Ba 0.95 Pb 0.05 TiO 3. The addition of Co 3+ ions results in a broadening of dielectric anom- alies related to the transition to p araelectric cubic phase, and the structural transition between the tetragonal and the orthorhombic phases. At low temperatures (125 – 200 K) the dielectric absorp- tion of Co-doped Ba 0.95 Pb 0.05 TiO 3 ceramics was fo…
Magnetic and electronic properties of double perovskites and estimation of their Curie temperatures byab initiocalculations
2008
First principles electronic structure calculations have been carried out on ordered double perovskites Sr_2B'B"O_6 (for B' = Cr or Fe and B" 4d and 5d transition metal elements) with increasing number of valence electrons at the B-sites, and on Ba_2MnReO_6 as well as Ba_2FeMoO_6. The Curie temperatures are estimated ab initio from the electronic structures obtained with the local spin-density functional approximation, full-potential generalized gradient approximation and/or the LDA+U method (U - Hubbard parameter). Frozen spin-spirals are used to model the excited states needed to evaluate the spherical approximation for the Curie temperatures. In cases, where the induced moments on the oxy…