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We examined the effect of Pb substitution in the layered superconductor LaO0.5F0.5Bi1−xPbxS2 (x = 0–0.15) through the measurements of the resistivity, thermal expansion, specific heat, and Seebeck coefficient. These transport and thermal properties show anomalies at certain temperatures (T*) for x ≥ 0.08. The large thermal expansion anomalies, specific heat anomalies, and the existence of hystereses in the above measurements indicate a first-order structural phase transition at T*. Additionally, the Seebeck coefficient indicates that the anomalies at T* are related not only to the lattice system, but also to the electronic system. Superconductivity is not observed above 2 K at x = 0.08, which is around the phase boundary where T* vanishes. The suppression of superconductivity around the structural phase boundary suggests a close relationship between the lattice and superconductivity. [ABSTRACT FROM AUTHOR]

We studied the effects of chemical pressure on Gd1−yRyMn0.7Co0.3O3 (R = nonmagnetic rare-earth element) with y = 0.1, 0.3, and 0.5. The substitution of Gd with La, Y, or Lu in orthorhombic Gd1−yRyMn1−xCoxO3 induced a systematic change in the unit-cell volume. Our results reveal that increasing or decreasing the average ionic radius of the rare-earth element in the compound affects the magnetic ordering temperature TC. The reduction in the proportion of Gd owing to substitution by nonmagnetic elements weakens the spin reversal effect. [ABSTRACT FROM AUTHOR]

We measured the low-temperature specific heat Cp, resistivity ρ, and magnetoresistance Δρ(H)/ρ(0) for amorphous Ce50Al50 synthesized by a DC high-rate sputter method. The low-temperature Cp (T < 2 K) decreases rapidly toward 0 K and has no indication of phase transition. The value of γ0 which is extrapolated down to 0 K of the Cp/T is 117 mJ/molK2. The temperature dependence of ρ increases with decreasing temperature down to 0.6 K. We found that both a weak localization effect and a coherent Kondo state might be realized in the low-temperature region for the present alloy from the conductivity analysis. Furthermore, in the low-temperature ρ, a T2 term with a very large coefficient A was observed. The ratio of A/γ02 is 0.63 ×10-5 (μΩcm/K2)/(mJ/molK2)2 and is near the value of typical Ce-based heavy-fermion compounds. The magnetoresistances Δρ(H)/ρ(0) at 0.5 K and 2 K are almost constant in the magnetic field region of H < 10 kOe. We considered that the negative magnetoresistance effect is due to the weak localization and the positive magnetoresistance to the heavy-fermion state in the present alloy. [ABSTRACT FROM AUTHOR]

We measured the magnetic susceptibility χ, electrical resistivity ρ, and specific heat Cp of a sputtered amorphous (a-)CeRu2Al10 alloy. χ value for a-CeRu2Al10 alloy follows a Curie-Weiss paramagnetic behavior in the high-temperature region, and magnetic transition was not observed down to 2 K. The effective paramagnetic moment peff is 1.19 μB/Ce-atom. The resistivity shows a typical disordered alloy behavior, that is, small temperature dependence for the whole temperature range. We observed an enhancement of ρ and Cp/T in the low-temperature region of T<10 K. The enhancement in ρ is suppressed by applying a magnetic field. It is suggested that this behavior is caused by the Kondo effect. [ABSTRACT FROM AUTHOR]

In this article, we discuss the electronic phase diagram of a high-Tc cuprate La2−xSrxCuO4; namely, how the electronic property changes as functions of temperature T and hole-doping level p. In particular, we focus on four crossover lines, which can be seen in the T dependences of uniform magnetic susceptibility and electronic specific heat. One of them is crossover line Ta(p) in the low doping region below p∼0.05 near the margin of the superconducting regime, which is associated with strongly developed antiferromagnetic (AF) spin correlations within the Cu–O planes. The others are crossover lines Tmax(p), T&ast;(p) and Tsf(p) in the normal state in the superconducting regime (0.05 Tmax>T&ast;>Tsf>Tc. It is suggested that crossover lines Tmax(p), T&ast;(p) and Tsf(p) will be associated with the gradual developments of AF spin correlations, a kind of precursor of superconductivity and superconducting critical fluctuations, respectively. [Copyright &y& Elsevier]