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Abstract: We report the synthesis, (micro)structure, magneto-transport and magnetization of polycrystalline La2/3Ca1/3MnO3:Ag x composites with , 0.1, 0.2, 0.3 and 0.4. The temperature coefficient of resistance (TCR) near ferromagnetic (FM) transition is increased significantly with the addition of Ag. The FM transition temperature is also increased slightly with Ag addition. Magneto-transport measurements revealed that magneto-resistance MR is found to be maximum near . Further the increased MR of up to 60% is seen above 300 K for higher silver added samples in an applied field of 7 T. Sharp TCR is seen near with the highest value of up to 15% for Ag(0.4) sample, which is an order of magnitude higher than the present pristine sample and the best value yet reported for any polycrystalline LCMO compound. Increased TCR, and significant above room temperature MR of La2/3Ca1/3MnO3:Ag x composites is explained on the basis of improved grain size and connectivity with silver addition in the matrix. Better coupled FM domains and nearly conducting grain boundaries give rise to improved physical properties of the La2/3Ca1/3MnO3 manganites. [Copyright &y& Elsevier]

Abstract: We carefully studied the nonsuperconducting sample of the magneto-superconducting RuSr2(Eu1−x Ce x )Cu2O10−δ series with composition RuSr2EuCeCu2O10−δ . This compound seems to exhibit a complex magnetic state as revealed by host of techniques like resistivity, thermopower, magnetic susceptibility, and MR measurements. The studied compound exhibited ferromagnetic like M(H) loops at 5, 20, and 50K, and semiconductor like electrical conduction down to 5K, with −MR 7T of up to 4% at low temperatures. The −MR 7T decreases fast above 150K and monotonically becomes close to zero above say 230K. Below, 150K −MR 7T decreases to around 3% monotonically down to 75K, with further increase to 4% at around 30K and lastly having a slight decrease below this temperature. The thermopower S(T) behavior closely followed the −MR 7T steps in terms of d(S/T)/dT slopes. Further, both MR 7T steps and d(S/T)/dT slopes are found in close vicinity to various magnetic ordering temperatures (T mag) of this compound. [Copyright &y& Elsevier]

A Tb-123 phase with the composition, TbSr2Cu2.7Mo0.3O7+δ, has been synthesized in single-phase form by the solid-state reaction route. Its phase purity has been confirmed from neutron powder diffraction studies. The as-synthesized Tb-123 sample does not show superconductivity down to 5 K. On the other hand, an unusually high antiferromagnetic ordering temperature (TN) of around 7 K is seen for the Tb moments. After 120-atm-O2 post-annealing, bulk superconductivity is achieved in this compound with a superconducting transition temperature (Tc) of about 30 K, without any significant effect on TN. To achieve higher oxygen content and higher Tc, the as-synthesized sample was subjected to high-pressure oxygenation, carried out in a closed cell, at 5 GPa and 400 °C in the presence of AgO as an excess-oxygen source. This sample exhibited superconductivity onset at around 80 K with a Meissner fraction larger than 10% at 5 K. Our observation of superconductivity at 80 K is the highest Tc to-date for the Tb-123 type compounds. [Copyright &y& Elsevier]