Upper Critical Magnetic Field of Superconducting Films with Magnetic Impurities.

The resistance of In-Mn and Pb-Mn alloys films was used to determine the upper critical magnetic field of these semiconductors. The measurements obtained were compared with the theory of Fulde and Maki which predicts that the pair-breaking effects of the magnetic impurities is temperature-independent, and that the pair-breaking effects of the magnetic impurities and the applied magnetic field are additive. Furthermore, it predicts explicitly the temperature dependence of H sub c2. The temperature dependence of H sub c2 for the In-Mn alloy films is well described by the Fulde-Maki theory, despite the moderately strong electron-phonon coupling and the strong interaction between the impurity spins and the conduction electron spins. The temperature dependence of H sub c2 for the Pb-Mn alloys films is not well described by the Fulde-Maki theory, probably due to the strong electron-phonon coupling in Pb.