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- Title
Effects of Metallic Spacer in Layered Superconducting Sr(MgTi)OFeAs.
- Authors
Lee, Kwan-Woo
- Abstract
The highly two-dimensional superconducting sys tem Sr(MgTi)OFeAs, recently synthesized in the range of 0.2≤ y≤0.5, shows an Mg concentration-dependent T. Reducing the Mg concentration from y=0.5 leads to a sudden increase in T, with a maximum T≈40 K at y=0.2. Using first principles calculations, the unsynthesized stoichiometric y=0 and the substoichiometric y=0.5 compounds have been investigated. For the 50 % Mg-doped phase ( y=0.5), Sr(MgTi)O layers are completely insulating spacers between FeAs layers, leading to the fermiology such as that found for other Fe pnictides. At y=0, representing a phase with metallic SrTiO layers, the Γ-centered Fe-derived Fermi surfaces (FSs) considerably shrink or disappear. Instead, three Γ-centered Ti FSs appear, and in particular two of them have similar size, like in MgB. Interestingly, FSs have very low Fermi velocity in large fractions: the lowest being 0.6×10 cm/s. Furthermore, our fixed spin moment calculations suggest the possibility of magnetic ordering, with magnetic Ti and nearly nonmagnetic Fe ions. These results indicate a crucial role of Sr(MgTi)O layers in this superconductivity.
- Subjects
SUPERCONDUCTORS; STOICHIOMETRY; NONMAGNETIC steel; ELECTRIC conductivity; SOLUTION (Chemistry)
- Publication
Journal of Superconductivity & Novel Magnetism, 2013, Vol 26, Issue 5, p1977
- ISSN
1557-1939
- Publication type
Article
- DOI
10.1007/s10948-012-2066-3