2012/09/07 by Salem-Sugui, S., Ghivelder, L., Alvarenga, A. D. +3
#FOS: Physical sciences #Superconductivity (cond-mat.supr-con)
paper · doi:10.48550/arxiv.1209.1594
Flux-creep data was obtained for fields along the second magnetization peak observed in M(H) curves of BaFe1.9Ni0.1As2 for H||c-axis. H||ab-planes and H forming a 45 degrees angle with ab-planes. The M-H loops from the different field directions can be collapsed onto a universal curve with a scaling factor equivalent to the superconducting anisotropy, showing that the pinning is three dimensional, although with remarkable differences in the vortex-dynamics as a function of field orientation. The resulting relaxation rate, R, when plotted as a function of field and temperature does not show any specific feature in the vicinity of the second magnetization peak field Hp, the relaxation shows a maximum at a field H2 well above Hp for H||c and a minimum at H^* for fields well below Hp for H||ab and H-45-ab. Isofield plots of the scaled activation energy obtained from flux-creep data at several different temperatures also do not show any evidence of a change in the pinning mechanism as the peak field is crossed. The Hp lines in the resulting phase diagrams do not appear to be consistent with a description-terms of a collective-plastic pinning crossover.