SUPERCONDUCTIVITY LOW-TEMPERATURE RESISTIVITY AND THERMOELECTRIC POWER OF DILUTE SOLID SOLUTION OF CE IN IN AND SN

被引:2
作者
BOATO, G
BUGO, M
RIZZUTO, C
机构
[1] Istituto di Fisica dell'Universita, Gruppo Nazionale Struttura della Materia, Genova
关键词
D O I
10.1063/1.2163642
中图分类号
O59 [应用物理学];
学科分类号
摘要
An interesting anomalous property of cerium metal is that its valence is not fixed, being able to be in a trivalent (magnetic) or in a tetravalent (nonmagnetic) state. It has been suggested that this, as well as the other anomalous properties of cerium, are due to the fact that the f-electrons are on external orbits, thus being able to interact with the conduction electrons in a similar manner to the d-electrons of the transition metals. If the f-electrons are not tightly bound in cerium metal, the possibility exists that dilute solid solutions of cerium in nontransition metals could induce the similar electron transport anomalies as transition metal impurities. We have measured the superconducting critical temperature Tc of In-Ce and Sn-Ce solid solutions as a function of the impurity concentration, as well as the resistivity and the thermoelectric power down to 0.3°K. An approximately linear decrease of Tc has been observed in both alloy systems up to the solid solubility limit (150 ppm at.). For In-Ce ΔTc/ρ is -8°K and for Sn-Ce ΔTc/ρ is -20°K, where ρ is the residual resistance ratio R4.2/ (R273-R 4.2) which varies linearly with concentration (c) and has the values of ρ/c = 0.31/at.% for the In-Ce system and ρ/c = 0.0471/at.% for the Sn-Ce system. The values of ΔTc/ρ are larger than would be expected on the basis of normal impurity scattering; however, the resistivity and thermoelectric power measurements do not indicate the presence of localized magnetic moments, the former showing no minimum and the latter being positive and small (S ≈ 0.3 mV/°K) for the present temperature range of measurements. We believe that if the assumption is made that a virtual f-level lies near the Fermi energy, the observed magnitude of the suppression of the superconducting critical temperature as well as the small positive thermopowers could be explained on the basis of existing theories. © 1968 The American Institute of Physics.
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页码:848 / &
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