Muon spin rotation studies ofSmFeAsO0.85andNdFeAsO0.85superconductors

Abstract

Measurements of the in-plane magnetic-field penetration depth ${\lambda }_{\text{ab}}$ in Fe-based superconductors with the nominal composition ${\text{SmFeAsO}}_{0.85}$ $\left(T_c\simeq 52\text{K}\right)$ and ${\text{NdFeAsO}}_{0.85}$ $\left(T_c\simeq 51\text{K}\right)$ were carried out by means of muon-spin rotation. The absolute values of ${\lambda }_{ab}$ at $T=0$ were found to be 189(5) and 195(5) nm for Sm and Nd substituted samples, respectively. The analysis of the magnetic penetration depth data within the Uemura classification scheme, which considers the correlation between the superconducting transition temperature $T_c$ and the effective Fermi temperature $T_F$, reveals that both families of Fe-based superconductors (with and without fluorine) fall to the same class of unconventional superconductors.