Mn Substitution Effect in Two-Gap Superconductor MgB_2(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

概要

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Mn substitution effects on normal and superconducting state of MgB_2 are reported. Although the superconducting transition temperature (T_c) radically decreases with Mn substitution, the E_<2g> phonon peak in Raman spectra shows no significant change, confirming that the T_c-suppression is not due to weakening of electron-phonon coupling by band-filling but due to the pair-breaking caused by magnetic scattering. In-plane resistivity indicates that Mn substitution introduces potential scattering, which is much stronger than the case of C and Al substitution. Nevertheless, the upper critical field H_<c2> is never enhanced by Mn-substitution. Based on this fact together with the behavior of H_<c2> anisotropy ratio, it is likely that strong potential scattering is introduced mainly in the π-bands. The effect of spin flip scattering other than the T_c suppression is not obvious.
社団法人日本物理学会の論文
2008-07-15