Effect of nano-NiO doping on the magnetic susceptibility and flux pinning in MgB<SUB align=right>2 superconductor

Abstract

Improving transport properties of polycrystalline MgB2 by nanoparticle doping has been widely studied by researchers. We have investigated the effect of nano-nickel (as nickel oxide) doping on the critical current density (Jc) of bulk MgB2 by measuring the ac susceptibility using locally made susceptometer. Samples were doped with nickel at 1%, 2%, 4%, 8% and 10% to investigate for the different quantities on the compound. We have studied the susceptibility as function of the amplitude of ac magnetic field and temperature. The uniformly distributed nano-Ni dopant replaced Mg ions only up to 2% and the rest was distributed uniformly throughout the material and served as pinning centres. Jc for the nano-Ni doped samples has been calculated from susceptibility data and was found to increase as we increased the Ni but saturates after 2%. Jc was enhanced by more than three times with doping. The little change in the XRD peak positions for MgB2 shown by XRD results indicated that Ni doping did not strongly affect the lattice parameters of MgB2. Susceptibility measurements reveals that Tc decreased from 37.7 for the pure sample down to 35.6 K for doped samples.