Difference between Al and C doping in anisotropic upper critical field development in MgB2

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Angst, M.
Bud'ko, Sergey L.
Wilke, R. H. T.
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American Physical Society
Canfield, Paul
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Physics and Astronomy
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Ames National Laboratory

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The temperature dependence of the upper critical field H-c2 for both field directions in partially substituted polycrystalline MgB2 was determined. Whereas the suppression of T-c is similar for aluminum and carbon substituted samples, H-c2 is affected by the substitution in profoundly different ways. In the case of Al substitution changes can tentatively be described by intrinsic effects (shift of the Fermi level). In the C substituted samples, H-c2 is increased drastically, and extrinsic effects (disorder) have to play a major role. The strong contrast between the two substitutions is discussed, taking into account three relevant scattering rates.
This article is published as Angst, M., S. L. Bud’ko, R. H. T. Wilke, and P. C. Canfield. "Difference between Al and C doping in anisotropic upper critical field development in Mg B 2." Physical Review B 71, no. 14 (2005): 144512. DOI: 10.1103/PhysRevB.71.144512. Copyright 2005 American Physical Society. Posted with permission.