Enhanced upper critical field, critical current density, and thermal activation energy in new ytterbium doped CeFeA_0.9F_0.1 superconductor

Abstract

In this report, we have investigated the essential physical properties of Ce_0.7Yb_0.3FeAsO_0.9F_0.1 superconductor such as field dependent critical current density (J_c), thermal activation energy (U₀), and upper critical field (H_c2). From the isothermal magnetization curves and size of the superconducting grains, the critical current density J_c of 2.3 × 10⁶ A/cm² at 2 K, 0.5 T was estimated using the Bean's model for this Yb doped superconductor. A gradual decrease of J_c and absence of peak effect were found on increasing magnetic field up to 5 T. Thermal activation energy (U₀/k_B = ∼2500 K) calculated from Arrhenius plots at low magnetic field (0.5 T) indicates a strong flux pinning potential might be co-existing with applied magnetic field. Our results suggest that this new Yb doped superconductor is a possible practical high temperature superconductor under certain magnetic field and temperature.