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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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A Gurtu P K Malhotra I S Mittra P M Sood SC Gupta VK Gupta GL Kaul LK Mangotra Y Prakash NK Rao ML Sharma 《Pramana》1974,3(5):311-322
This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR em = 〈n s〉/〈n ch〉, where 〈n ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R em = 1·71 implies an effectiveA-dependence ofR A =A 0.18,i.e., a very weak dependence. Predictions ofR em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production. 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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