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Abstract: Detailed X-ray diffraction studies on RuSr2Eu1.5Ce0.5Cu2O10−δ (Eu–Ru-1222) magneto superconductor down to 13K at close temperature intervals revealed that with decreasing temperature, the c-parameter decreases linearly down to 100K, following the relation c =28.412(1)+2.5(1)×10−4 T and then becomes almost temperature independent on further lowering of temperature. Interestingly, the linear decrease in the a-parameter is seen only up to 180K. Below 180K, the observed values of the a-parameters are more than the value expected from the linear variation. This departure can be considered as development of strain in the system. Interestingly enough, these temperatures coincide with the complex magnetic ordering (T mag) of Ru in Ru-1222 system. This is the first report of the observation of the onset of excess volume and also of the strain along the a-axis near the magnetic ordering temperature in Ru-1222 superconductor, and indicates a coupling between the lattice and the magnetism in this system. Magnetization, magneto transport and thermoelectric power measurements being carried out on the same sample are also reported. The results of low temperature excess volume and the strain along a-axis of Ru-1222 compound are reportedly not seen in Ru-1212 (RuSr2GdCu2O8). [Copyright &y& Elsevier]

Abstract: We report properties of the Zn-substituted polycrystalline superconductors BaFe1.87− x Zn x Co0.13As2 (x =0, 0.04, 0.06 and 0.08) prepared at ambient pressure condition. Electrical conductivity and magnetization measurements revealed that the superconductivity is suppressed by at most 2% substitution of Zn, which shows typical behavior of an anisotropically gaped superconductivity rather than an isotropically gaped superconductivity. With increasing the amount of Zn, weak change in superconductivity was observed. It is likely impossible to obtain BaFe1.87− x Zn x Co0.13As2 crystals with x >0.04 at ambient pressure condition. On the basis of the structural and the physical properties of the present system, we discuss a possible mechanism of the superconducting pairing. [Copyright &y& Elsevier]