Vortex fluctuation effect evaluated using reversible magnetization in optimally doped single crystal NaFe0.97Co0.03As superconductor

Abstract

The reversible magnetization curves for various magnetic fields are investigated for a single crystal of the optimally doped NaFe0.97Co0.03As superconductor with the superconducting transition temperature Tc=20.9 K (ρ(T)=0) in the case where H is parallel to c-axis. A well-formed rounding effect is observed in the temperature dependence of the magnetization, and it widens on increasing the strength of the applied magnetic fields. At 20.2 K, we observe a crossing of the M(T) curves for different applied magnetic fields, indicating important fluctuation effects. The irreversibility line Hirr(T) obeys a universal scaling relation Hirr(T)=H0(1-T/Tc)ncharacterized by n∼1.537, which confirms the moderately anisotropic nature of the sample. The scaling analysis of the reversible magnetization in the region near Tc(H) supports the three-dimensional nature of the vortex fluctuations in NaFe0.97Co0.03As. © 2014 IOP Publishing Ltd.