Flux-flow and vortex-glass phase in iron pnictide single crystals with K

Abstract

We analysed the flux-flow region of isofield magnetoresistivity data obtained on three crystals of NixAs2 with Tc ∼ 20 K for three different geometries relative to the angle formed between the applied magnetic field and the c-axis of the crystals. The field dependent activation energy, U0, was obtained from the thermal assisted flux-flow (TAFF) and modified vortex-glass models, which were compared with the values of U0 obtained from flux-creep available in the literature. We observed that the U0 obtained from the TAFF model show deviations among the different crystals, while the correspondent glass lines obtained from the vortex-glass model are virtually coincident. It is shown that the data is well explained by the modified vortex-glass model, allowing extract of values of Tg, the glass transition temperature, and , a temperature which scales with the mean field critical temperature . The resulting glass lines obey the anisotropic Ginzburg–Landau theory and are well fitted by a theory developed in the literature by considering the effect of disorder.