We investigated the effect of alloying on the upper critical field Hc2 in 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 Hc2(T). Record high values of Hc2⊥(4.2)≃35T and Hc2∥(4.2)≃51T were observed perpendicular and parallel to the ab plane, respectively. The temperature dependence of Hc2(T) is described well by a theory of dirty two-gap superconductivity. Extrapolation of the experimental data to T=0 suggests that Hc2∥(0) approaches the paramagnetic limit of ∼70T.
@article{arxiv.cond-mat/0402001,
title = {High-field superconductivity in alloyed MgB2 thin films},
author = {V. Braccini and A. Gurevich and J. E. Giencke and M. C. Jewell and C. B. Eom and D. C. Larbalestier and A. Pogrebnyakov and Y. Cui and B. T. Liu and Y. F. Hu and J. M. Redwing and Qi Li and X. X. Xi and R. K. Singh and R. Gandikota and J. Kim and B. Wilkens and N. Newman and J. Rowell and B. Moeckly and V. Ferrando and C. Tarantini and D. Marre and M. Putti and C. Ferdeghini and R. Vaglio and E. Haanappel},
journal= {arXiv preprint arXiv:cond-mat/0402001},
year = {2009}
}