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M. Eisterer, C. Krutzler, M. Zehetmayer, H. W. Weber, S. Kazakov, J. Karpinski:
"Influence of Carbon Doping on the Reversible Magnetization of MgB₂ Single Crystals";
Poster: Int. Conf. on Materials and Mechanisms of Superconductivity and High Temperature Superconductivity (M2S), Dresden (Deutschland); 2006-07-09 - 2006-07-14.

The reversible magnetization of Mg(B1-xCx)2 single crystals with varying carbon content (x=0-0.095) was measured by SQUID magnetometry. It was found to be strongly influenced by the two-band character of this material. At low magnetic fields charge carriers of both bands contribute to superconductivity and to diamagnetism. At high fields the p-band is suppressed and the s-band mainly determines the magnetization. This allows us to extract information on both bands by analyzing the reversible magnetization in terms of two band Ginzburg-Landau (GL) theory. The "intrinsic" magnetic penetration increases in both bands with increasing carbon content, but the s-band remains crucial for the upper critical field. Changes of the field dependence of the resulting "effective" penetration depth by carbon doping are discussed.