Mixed-state transport characteristics of magnesium diboride films

AUTOR(ES)

Kunchur, M. N., Cheng, Wu, Arcos, D. H., Saracila, G., Eun-Mi, Choi, Kim, Kijoon H.P., Kang, W. N., Sung-Ik, Lee

FONTE

Brazilian Journal of Physics

DATA DE PUBLICAÇÃO

2003-12

RESUMO

We have investigated the low-temperature (T < Tc=10) mixed-state current-voltage (IV) response of magnesium diboride films beyond the point where the superconductivity is completely destroyed and the system enters the normal state. The resistance-versus-current R(I) curves are extremely steep and featureless, with a critical current density j c, marking the onset of dissipation, that is unusually high (j c>j d/10) with respect to the depairing current density j d. At large flux densities Hc2/10 $\lessim$ B $\lessim$Hc2, the R(I) curve has a functional shape that is largely independent of B, indicating that the rise in resistivity with increasing current occurs mainly due to pair-breaking rather than flux motion. The macroscopic destruction current I*, which drives the system normal, has a B/Hc2: $\sqrt{B/H_{c2}}$ flux-density dependence, suggesting that the vortices mainly reduce the effective cross section over which a current of effective density j ~ j d flows.

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