Systematic Study of Vortex Pinning and a Liquid–Glass Phase Transition in BaFe2–x Ni x As2 Single Crystals

The vortex pinning and liquid-glass transition have been studied in BaFe2–xNixAs2 single crystals with different doping levels (x = 0.065, 0.093, 0.1, 0.14, 0.18). We found that Ni-doped Ba-122 has rather narrow vortex-liquid state region. Our results show that the temperature dependence of the resistivity as well as I−V characteristics of Ni-doped Ba-122 is consistent with 3D vortex-glass model. It was found that -pinning gives the main contribution to overall pinning in 122 Ni-doped system. The vortex phase diagrams for different doping levels were built based on the obtained data of temperature of the vortex-glass transition Tg and the upper critical magnetic field Hc2.