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Ozaki T.,Japan National Institute of Materials Science | Ozaki T.,Transformative Research Project on Iron Pnictides | Deguchi K.,Japan National Institute of Materials Science | Deguchi K.,Transformative Research Project on Iron Pnictides | And 6 more authors.
Physica C: Superconductivity and its Applications | Year: 2011

We fabricated FeTe0.5Se0.5 superconducting wires using ex-situ Powder-in-tube method with an Fe sheath. It was amazing that superconducting current was observed in the as-drawn wire without any heat treatments. By heat treatment at 200 °C for 2 hours, Tczero and J c at 4.2 K were enhanced up to 9.1 K and 64.1 A/cm2 (Ic = 182.6 mA), respectively. Furthermore, the Jc of FeTe0.5Se0.5 wire heat treated at 200 °C for 2 h was not much sensitive to the applied magnetic fields. Therefore, FeTe 0.5Se0.5 wires have a great potential for applications. © 2011 Elsevier B.V. All rights reserved. Source


Mizuguchi Y.,Japan National Institute of Materials Science | Mizuguchi Y.,Transformative Research Project on Iron Pnictides | Mizuguchi Y.,University of Tsukuba | Tomioka F.,Japan National Institute of Materials Science | And 10 more authors.
Physica C: Superconductivity and its Applications | Year: 2010

We investigated the pressure effects on the FeSe superconductor and the related compounds. Pressure dependence of superconducting transition temperature (Tc) for FeSe0.8S0.2 exhibits a dome-shaped behavior below 0.76 GPa. On the other hand, the Tc of FeSe 0.25Te0.75 linearly increases up to 0.99 GPa. Here we discuss the relation between the physical pressure effects and the chemical pressure effects on the FeSe system. © 2009 Elsevier B.V. All rights reserved. Source


Mizuguchi Y.,Japan National Institute of Materials Science | Mizuguchi Y.,Transformative Research Project on Iron Pnictides | Mizuguchi Y.,University of Tsukuba | Furubayashi T.,Japan National Institute of Materials Science | And 10 more authors.
Physica C: Superconductivity and its Applications | Year: 2010

We carried out 57Fe Mössbauer measurements for FeSe and Fe1.08Te to investigate the magnetic properties. There was no sign of magnetic ordering above 4.2 K for superconducting FeSe. The magnetic sextet corresponding to antiferromagnetic ordering of Fe in low-spin state was observed for non-superconducting Fe1.08Te. © 2009 Elsevier B.V. All rights reserved. Source


Deguchi K.,Japan National Institute of Materials Science | Deguchi K.,University of Tsukuba | Deguchi K.,Transformative Research Project on Iron Pnictides | Mizuguchi Y.,Japan National Institute of Materials Science | And 13 more authors.
Physica C: Superconductivity and its Applications | Year: 2010

We observed dramatic improvement of the superconducting transition temperature in FeTe0.8S0.2. Although as-grown sample did not show zero resistivity, the sample, which was exposed to air for several days, showed zero resistivity with sharp superconducting transition. © 2009 Elsevier B.V. All rights reserved. Source


Ishida S.,University of Tokyo | Ishida S.,Japan National Institute of Advanced Industrial Science and Technology | Ishida S.,Transformative Research Project on Iron Pnictides | Nakajima M.,University of Tokyo | And 26 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

Characteristic normal-state charge transport is found in the oxygen-deficient iron-arsenides Ln FeAsO1-y (Ln: La and Nd) with the highest Tc's among known Fe-based superconductors. The effect of "doping" in this system is mainly on the carrier scattering, quite distinct from that in high- Tc cuprates. In the superconducting regime of the La system with maximum Tc =28 K, the low-temperature resistivity is dominated by a T2 term. On the other hand, in the Nd system with Tc higher than 40 K, the carriers are subject to stronger scattering showing T -linear resistivity and small magnetoresistance. Such strong scattering appears crucial for high- Tc superconductivity in the iron-based system. © 2010 The American Physical Society. Source

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