G. Prando, R. Giraud, M. Abdel-Hafiez, S. Aswartham, A. U. B. Wolter, S. Wurmehl, B. Büchner
Measurements of magnetic ac susceptibility were performed on a single crystal of superconducting Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ close to the conditions of optimal doping. The extremely high quality of the investigated sample allows the detection of dynamical-scaling behaviour associated with a glass transition for the flux lines in the limit of weak degree of quenched disorder. The corresponding critical exponent and glass critical temperature are precisely quantified for different values of the polarizing magnetic field up to 9 Tesla. The field-dependence of the critical exponent rules out any dimensionality crossover for the vortex state in the investigated range, suggesting instead a gradual transition among qualitatively different types of glassy phases. In particular, a Bragg-like glass is likely to be gradually disordered towards a more amorphous state with increasing the magnetic field.
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http://arxiv.org/abs/1207.2457
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