We investigated the effect of alloying on the upper critical field Hc2 for 12 MgB2 films, in which disorder was introduced by growth, carbon doping or He-ion irradiation, finding a significant Hc2 enhancement in C-alloyed films, and an anomalous upward curvature of Hc2sTd. Record high values of Hc2 's4.2d<35 T and Hc2 is4.2d<51 T were observed perpendicular and parallel to the ab plane, respectively. The temperature dependence of Hc2sTd is described well by a theory of dirty two-gap superconductivity. Extrapolation of the experimental data to T=0 suggests that Hc2 is0d may approach the paramagnetic limit of ,70 T.
High-field superconductivity in alloyed MgB2 thin films
MARRE', DANIELE;PUTTI, MARINA;
2005-01-01
Abstract
We investigated the effect of alloying on the upper critical field Hc2 for 12 MgB2 films, in which disorder was introduced by growth, carbon doping or He-ion irradiation, finding a significant Hc2 enhancement in C-alloyed films, and an anomalous upward curvature of Hc2sTd. Record high values of Hc2 's4.2d<35 T and Hc2 is4.2d<51 T were observed perpendicular and parallel to the ab plane, respectively. The temperature dependence of Hc2sTd is described well by a theory of dirty two-gap superconductivity. Extrapolation of the experimental data to T=0 suggests that Hc2 is0d may approach the paramagnetic limit of ,70 T.
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