2007/04/26 by J. Karpiński, J. Karpinski, N. Zhigadlo +8
Materials Science · Physics and Astronomy · #Iron-based superconductors research #Superconductivity in MgB2 and Alloys #Thermal Expansion and Ionic Conductivity #cond-mat.mtrl-sci #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.77.214507
published as Phys. Rev. B 77, 214507 (2008) · 22 pages, 17 figures, submitted to PRB
arxiv created 2007/04/26 · openalex publication_date 2008/06/11 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The effect of Li substitution and Li-C co-substitution on the superconducting properties and crystal structure of MgB2 single crystals has been investigated. Hole doping with Li decreases the superconducting transition temperature Tc at a slower rate than that of the electron doping with C or Al. For crystals co-substituted with Li for Mg and C for B, Tc decreases more rapidly than for crystals substituted with C alone. This means that holes introduced with Li cannot counterbalance the influence of electrons doped with C and are not able to prevent Tc to decrease. The possible explanation is that holes coming from Li occupy mainly the \ensuremathπ band while electrons coming from C fill the \ensuremathσ band. The resistivity in both Li substituted and Li-C co-substituted crystals is significantly increased, reflecting scattering due to substitutional defects, including distortion of the lattice. Li substitution decreases the upper critical field Hc2(T)^\ensuremath∥ab while Hc2(T)^\ensuremath∥c does not change. The temperature dependences of Hc2 for the Li and Al single-substituted crystals with the same Tc show a similar Hc2(T) behavior despite the different substitution level.