1,720,981 research outputs found
Equiatomic ternary lanthanum-transition metal-tin phases: Structural and electrical results
No full textThe crystallographic parameters and electrical resistivity measurements in the 1.5–300 K temperature range for the LaXSn phases (X ≡ Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au) are reported. A change in structure with increasing group number of the transition metal is observed. A new superconducting compound, LaRhSn with Tc = 1.7 K, is detected by electrical resistivity measurements and confirmed by a.c. susceptibility data. A negative curvature in the thermal dependence of the electrical resistivity is observed for all compounds. A quantitative analysis of the experimental data using Mott's model and the phenomenological exponential approach is reported
THERMODYNAMIC AND PHYSICAL-PROPERTIES OF MIXED-VALENCE YBPDIN AND OF CAPDIN, SRPDIN, ERPDIN, EUPDIN INTERMETALLIC COMPOUNDS
No full textThe thermodynamic and physical properties (crystal structure, thermal expansion, magnetic properties and heat content)of YbPdIn and MPdIn ( M = Ca, Sr, Er, Eu) were measured over a wide temperature range (100-1000K) in order to expalin the anomalous behaviour of YbPdIn. The obtained results led to the determination of three previously unknown compounds (CaPdIn, SrPdIn and EuPdIn) which crystallise with the TiNiSi type structure. The anomalous behaviour of YbPdIb was found to depend on the instability of the valence which shows an almost regular change from divalency to trivalency with increasing temperature. An approximate determination of the energy required in this electronic process is also presented
Magnetocaloric effect in the intermetallic compound Gd7Pd3
No full textAs a part of a current research concerning the physical characterisation of Rare Earth intermetallic compounds for magnetic refrigeration devices, the magnetocaloric properties of the Gd7Pd3 phase, which shows a ferromagnetic transition at 318 K, are presented. Heat capacity measurements have been performed in the 5-360 K temperature range and for applied magnetic fields up to 5 T (Tesla). Basing on the heat capacity data the isothermal entropy change DeltaS(M) and the adiabatic temperature rise DeltaT(ad) have been calculated (DeltaS(M) = 2.5 and 6.5 J/K kg and DeltaT(ad) = 3.0 and 8.5 K at 320 K and respectively at 2 and 5 T). From the DeltaS(M) vs. T plot the refrigerant capacity in the 260-360 K temperature range has been calculated to be 100 J/kg for an applied magnetic field of 2 T and 380 J/kg for an applied magnetic field of 5 T
THE TH-TL PHASE-DIAGRAM AND THE ALLOYING PROPERTIES OF THORIUM WITH THE GROUP IIIB ELEMENTS
No full textThe phase diagram of the Th-Tl system has been examined over almost the whole composition range using differential thermal analysis (DTA) and X-ray analysis. Five intermediate phases have been found to exist: ThTl3 (AuCu3 type), Th3Tl5 (Pu3Pd5 type), ThTl (ThIn type), Th5Tl3 (Mn5Si3 type) and Th2Tl (CuAl2 type). Three eutectic points are also present in this system: 22.0 at.% Tl and 1080 °C; 60.5 at.% Tl and 1180 °C; less than 1.0 at.% Th and 295 °C.
The thorium-rich region of the diagram, up to 20 at.% Tl, has not been examined owing to the strong contamination of the alloys by the container material (molybdenum) and has been drawn on the basis of dimensional considerations and some DTA results.
The data obtained have been used to complete a general view of the alloying properties of thorium with the group IIIB elements
Structural anomaly in GdNiAl: a crystallographic, electric and magnetic investigation
No full textLow temperature electrical resistivity and X-ray powder diffraction measurements showed a transformation paint at about 200 K, attributed to a transition between two slightly different crystallographic forms of the ZrNiAl type. A corresponding anomaly was observed in the thermal behaviour of the magnetic susceptibility, and the results were analyzed in the framework of the RKKY theory. Ferromagnetic ordering occurs at 57 K, and two other transition temperatures, 30 and 14 K, were detected: these points, as already observed for TbNiAl, DyNiAl and HoNiAl may be imputed to order-order magnetic transitions
HIGH-TEMPERATURE BEHAVIOR OF THE MIXED-VALENCE COMPOUNDS EUCU2SI2, YBCU2SI2 AND THE REFERENCE COMPOUNDS CACU2SI2 AND GDCU2SI2
No full textSome physical properties (thermal expansions, magnetic susceptibilities and heat contents) of EuCu2Si2, YbCu2Si2 and reference compounds CaCu2Si2 and GdCu2Si2 have been measured in the temperature range 300–1000 K. The results obtained together with previous findings show that the valence of EuCu2Si2 is strongly dependent on T (valency, 2.9 at 100 K to 2.3 at 1000 K) while YbCu2Si2 maintains an almost constant valence value of 2.85, at least from 300 to 1000 K. For EuCu2Si2 an approximate determination of the energy required in the electronic process involved is also presented
HIGH-TEMPERATURE BEHAVIOR OF UNSTABLE EUPD2SI2 AND REFERENCE MPD2SI2 COMPOUNDS (M = ALL RARE-EARTHS AND ALKALINE-EARTHS)
No full textThermal behaviour and lattice parameters were determined for all RPd2Si2 compounds together with CaPd2Si2 and SrPd2Si2 (ThCr2Si2-type) phases.
The fluctuating valence system EuPd2Si2 was investigated in the temperature range 100–800 K. Its lattice constants were compared with those for the reference compounds CaPd2Si2 and GdPd2Si2 and the fractional valence was derived at each temperature.
Magnetic susceptibility measurements in the same temperature range confirmed the sharp valence change from 2.7 to 2.3 between 150 and 200 K and a room temperature value of 2.27
Electrical resistivity measurements of some R5Si3 phases: R = Gd, Tb, Yb, Lu and Y
No full textThe electrical resistivity of the R5Si3 phases with R = Gd, Th, Yb, Lu, Y has been measured in the 10-800 K temperature range. The compounds of Gd and Th exhibit one transformation point, which can be ascribed to magnetic transitions. The temperature dependence of the resistivity of Y5Si3 and Lu5Si3 has been described by a combination of the phonon contribution and an interband scattering term. For Yb5Si3, the different behaviour in the electrical resistivity, the low value of the magnetic moment as well as the anomalous values of the elementary cell constants can be explained assuming a mixed valent state of Yb: a divalent Yb ion in one site set and a trivalent Yb ion in the other site
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