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The interaction of the components in the Ce–Pt–Si system at 600 °C was investigated over the whole concentration range by X-ray powder and single crystal diffraction, DTA, and electron probe X-ray analysis. There are nine ternary compounds in the Ce–Pt–Si system. The crystal structures of eight of them were determined.

The crystal structures of the new compounds Ce 2 Rh 12 Si 7 and Ce 6 Rh 30 Si 19 , extracted from an ingot of composition Ce 9.5 Rh 56.9 Si 33.6 , were investigated by X-ray single crystal diffraction methods. The title compounds crystallize in the hexagonal space group P 6 3 / m with unit cell parameters a =9.706(1) A, c =3.8394(3) A and a =15.698(2) A, c =3.8571(4) A, respectively. Ce 2 Rh 12 Si 7 and Ce 6 Rh 30 Si 19 represent members of a family of hexagonal structures with a short unit cell parameter c ≈3.7 A and with general formula R n ( n +1) T 6( n 2 +1) M 4 n 2 +3 , where R is the rare earth, T the transition metal, and M the element of the IV or V main group. Ce 2 Rh 12 Si 7 crystallizes with the Ho 2 Rh 12 As 7 type, ignoring the disordered arrangement of non-metal atoms on the c -axis. The structure of Ce 6 Rh 30 Si 19 is closely related to that of Sc 6 Co 30 Si 19 .

CePt3Si is a novel heavy fermion superconductor, crystallizing in the CePt3B structure as a tetragonally distorted low symmetry variant of the AuCu3 structure type. CePt3Si exhibits antiferromagnetic order at T(N) approximately 2.2 K and enters into a heavy fermion superconducting state at T(c) approximately 0.75 K. Large values of H(')(c2) approximately -8.5 T/K and H(c2)(0) approximately 5 T refer to heavy quasiparticles forming Cooper pairs. Hitherto, CePt3Si is the first heavy fermion superconductor without a center of symmetry.

CePt3Si exhibits antiferromagnetic order at T N ≈ 2.2 K and superconductivity (SC) at T c ≈ 0.75 K. Large values of H′ c2 ≈ −8.5 T/K and H c2(0) ≈ 5 T indicate Cooper pairs formed out of heavy quasiparticles. The mass enhancement originates from Kondo interaction with a characteristic temperature T K ≈ 8 K. NMR and μSR measurements evidence coexistence of SC and long-range magnetic order on a microscopic scale. Moreover, CePt3Si is the first heavy-fermion SC without an inversion symmetry. This gives rise to a novel type of the NMR relaxation rate 1/T 1 never reported before for other heavy-fermion superconductors. Studies of Si/Ge substitution allow us to establish a phase diagram.

The new cerium ternary compounds Ce/sub 3/Pt/sub 4/Ge/sub 6/ and Ce/sub 2/Pt/sub 7/Ge/sub 4/ with novel crystal structure types have been prepared and characterized. We present transport and magnetic properties of these compounds in temperature range (2-300) K. Behavior of resistivity and magnetisation is similar, both compounds demonstrate Kondo-like features and possible magnetic transition near the helium temperature. >

The new ternary compound with giant unit cell La117Ru57Sn112 has been yielded by interaction between pure components lanthanum, ruthenium and tin and investigated by X-ray diffraction and scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDX) means. Previously, intermetallics with cobalt of similar composition and structure were found in the ternary systems and Dy-Co-Sn and Pr-Co-Sn – Dy117Co57Sn112 and Pr117Co57Sn112 respectively [1, 2]. The intermetallic La117Ru57Sn112 crystallizes in a cubic Dy117Co57Sn112 type structure with space group Fm-3m (No. 225) and lattice parameter a = 31.529(5). A single-crystal suitable for the X-ray measurements was isolated from the of the equiatomic alloy La33.3Ru33.3Sn33.4. The structure was solved by means of direct methods and refined using the SHELXS-97 and SHELXL-97 programs (R1 = 0.033 for 1042 Fo > 4σ(Fo) and 0.061 for all collected data). The additional sample of the La40.2Ru19.9Sn39.9 composition was prepared and investigated X-ray by powder diffraction technique (CuKα1 radiation, 5 < 2Θ < 900). The collected intensities data were refined by the Rietveld method using the La117Ru57Sn112 single crystal model and FullProf program. Based on a minimum of differences between the observed and calculated theoretically intensities one can judge the good convergence results.

The ferromagnetic heavy fermion compound Ce3RhSi3 was studied by means of electrical resistivity, Hall effect, thermoelectric power and Nernst coefficient measurements. Below T ≈ 30 K, all the transport characteristics were found to behave anomalously as functions of temperature and magnetic field. In particular, the Hall and Nernst coefficients at low temperatures exhibit pronounced and strongly field-dependent maxima, likely possessing the same microscopic origin, which however cannot be captured by available theoretical models.

A polycrystalline sample of Ce3Pd20Ge6 is investigated using a dc SQUID magnetometer. A noticeable difference between ZFC and FC magnetic susceptibility is found below ≈60 K. The temperature dependence of the magnetic susceptibility demonstrates an anomaly near approximately 2.8 K below which a remanent magnetic moment exists. Two characteristic temperatures detected support the assumption that there are different cerium magnetic subsystems in Ce3Pd20X6 (X=Ge, Si) compounds. Unusual magnetic behavior observed in Ce3Pd20Ge6 is discussed within the framework of the “molecular magnetism” model which predicts a frustration of exchange interactions.

UESTRO intento es analizar aqui un texto de Machado, operando, por lo general, con el material del mismo texto sin recurrir a asociaciones literarias fuera de este. Sin embargo, en ciertos casos nos permitimos expresar unas observaciones de carActer facultativo e hipotitico en notas al pie de la p gina. El poema de Machado se encuentra entre otros dedicados a las temporadas del afio: "En abril las aguas mil," "Amanecer de otofio," "Noche de verano"; podemos, pues, percibirlo dentro de un ciclo poetico referente al tiempo anual e insertado entre otros poemas dedicados a las "tierras." "Pascua de Resurrecci6n" cuenta con 22 versos y rima asonante