• S J Singh

      Articles written in Journal of Chemical Sciences

    • Superconductivity at 31.3 K in Yb-doped La(O/F)FeAs superconductors

      J Prakash S J Singh S Patnaik A K Ganguli

      More Details Abstract Fulltext PDF

      The effect of ytterbium substitution at the lanthanum site on the superconducting properties of La$_{1-x}$Yb$_x$O0.8F0.2FeAs ($x = 0.10$, 0.20 and 0.30) oxypnictides has been investigated. Powder X-ray diffraction studies show the presence of Yb2O3 and LaOF as secondary phases. The superconducting transition temperature ($T_c$) of 31.3 ($\pm \, 0.05$) K has been observed in $x = 0.1$ composition which is the maximum $T_c$ so far in the La(O/F)FeAs superconductor family at ambient pressure. Further increase in 𝑥 leads to suppression and broadening of superconducting transition. The resistive transition curves under different magnetic fields were investigated, leading to determination of upper critical field $H_{c2}$ (𝑇) of this new superconductor. The value of $H_{c2}$ at zero temperature is estimated to be about 46 T corresponding to coherence length ∼ 27 Å.

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