Critical current density and magnetic phase diagram of BaFe1.29Ru0.71As2   Single Crystals
  The critical current density has been measured on single crystals of Ru substituted BaFe2As2 superconductor at several temperatures and in fields up to 16 T. The magnetisation versus field isotherms reveal the occurrence of a clear second magnetisation peak (SMP) also known as fish-tail effect for both H parallel and perpendicular to c-axis of the crystal. The in-field resistance and magnetisation data are used to put forth a vortex phase diagram. The nature of the vortices have been determined from scaling behaviour of the pinning force density extracted from the Jc-H isotherms. The scaled JC versus reduced temperature behaviour seems to fit to a power law that indicates unambiguously that pinning in this system arises due to the spatial variation in the mean free path, viz. delta-l pinning. 
Shilpam Sharma, K. Vinod, C. S. Sundar and A. Bharathi
cond-mat.supr-con