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Il Nuovo Cimento D - In this work the thermal conditions required for single-crystal growth in RBa2Cu3O7−x systems (R=Y or rare earths apart from Ce and Tb) have been systematically revised... 相似文献
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Thermal expansion coefficient between 77 and 900K, isothermal compressibility in the 0–80 Kbar pressure range, magnetic susceptibility between 77 and 1300 K and heat capacity at constant pressure in the 20–300 K temperature range were determined for the LaSn3 compound. From the experimental data, the specific heat at constant volume was calculated and the thermal dependence of the Debye's parameter θD was obtained. The electron contribution to the heat capacity was also determined from the high temperature data. The magnetic properties confirm that there is no evidence of the existence of a magnetic moment localized on La atoms, in contrast with a previous report and in agreement with the general assumptions. A little anomaly found in the expansion coefficient, in the isothermal compressibility and in the specific heat is discussed in terms of a lattice order-disorder phenomenon. 相似文献
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D. D. Sarma W. Speier L. Kumar C. Carbone A. Spinsanti O. Bisi A. Iandelli G. L. Olcese A. Palenzona 《Zeitschrift für Physik B Condensed Matter》1988,71(1):69-74
The electronic properties of calcium silicides (CaSi and CaSi2) are investigated through a joint experimental and theoretical study using Bremsstrahlung Isochromat spectroscopy (BIS) and self-consistent calculation of the electronic states by the Linear Muffin-Tin Orbitals (LMTO) method in the Atomic Sphere Approximation (ASA). The peculiar crystal structure of CaSi2 with two inequivalent Si atoms is responsible for a well defined BIS feature. We found that the calculated high energy DOS features are consistently lower in energy compared to the BIS spectra. Inclusion of the cross-sections of different states into the calculations improves the agreement between the experimental spectra and the calculated curve. We also show that considerable covalent character is present in the bond of calcium silicides. 相似文献
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The lighter rare earth-cobalt and thorium-cobalt binary systems were revised on the rare earth or thorium side, by metallographic, electron microprobe and X-ray methods. In agreement with previous works, it is confirmed that, in these systems, the first intermetallic compound corresponds to the following stoichiometry: 3:1 for trivalent La, Pr and Nd; 7:3 for tetravalent Th; 24:11 for Ce. The electronic structure of Ce in the hexagonal (P63mc) Ce24Co11 phase was investigated via magnetic susceptibility measurements in the 4.2–1300 K temperature range. The results show that the Curie-Weiss law is not followed, no magnetic order occurs down to 4.2 K and a very small change in the thermal behaviour of the magnetic susceptibility appears above the melting point of the phase (750 K). The abnormally low values of the magnetic susceptibility of Ce24Co11 could be understood by assuming Co is a non-magnetic state and Ce in a temperature dependent mixed valence state. 相似文献
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Gli autori riferiscono intorno a misure delle proprietà diamagnetiche di superconduttori ad alta temperatura, siano monocristalli
o polveri, mediante un nuovo levitometro magnetico. Il nuovo strumento ha consentito di: 1) determinare la diminuzione della
magnetizzazione e della suscettività al crescere del campo magnetico nei cuprati di ittrio e bario; 2) confrontare il comportamento
delle polveri con quello del monocristallo; 3) analizzare lo spettro di suscettività e la struttura dei flussoidi dei grani
levitanti. Lo strumento si è rivelato essere un ottimo spettrometro magnetico adatto alla separazione di qualità delle diverse
fasi superconduttrici presenti nei grani. (A cura dell'editore).
(Conferenza tenuta dal Prof. G. Morpurgo il 27 marzo 1990) 相似文献
(Conferenza tenuta dal Prof. G. Morpurgo il 27 marzo 1990) 相似文献
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We have measured on the CeSn3 compound, the expansion coefficient between 80 and 800 K at normal pressure, the isothermal compressibility in the 0–8 GPa pressure range at room temperature and the heat capacity at constant pressure in the 60–300 K temperature range. The experimental data were compared with those previously found for the isomorphous LaSn3 phase, assumed as a proper reference material for the study of the intermediate valency states in CeSn3. Both the thermal expansion (3α) and the isothermal compressibility (k) of CeSn3 show behaviours quite different from those of LaSn3: for instance, in the standard conditions, 3α is 55 × 10?6K?1for CeSn3 and 38 × 10?6K?1for LaSn3; k is 15 × 10?12 Pa?1 and 12 × 10?12 Pa?1 respectively for CeSn3 and LaSn3. The thermal behaviour of the molar specific heat at constant pressure of CeSn3 is similar to that of LaSn3 for temperatures lower than 50 K. In the 70–300 K temperature range, the heat capacity of CeSn3 is clearly higher than that of LaSn3, ΔCp being maximum near 150 K. The analysis of the calorimetric data show that the electronic coefficient γ of CeSn3 is temperature dependent: its value varies from 53 mJ K?2 mole?1 at low temperature 24 mJ K?2 mole?1 at 300 K. 相似文献