Pure and substituted single crystals of the two-gap MgB₂ superconductor have been grown at a pressure of 30 kbar at temperature 1800-2000°C using the cubic anvil technique. High crystals' quality expresses as low residual resistivity ρ_o(40 K) = 0.5 μΩcm. Magnetic (Mn, Fe) and non-magnetic (Li, Al, C) ions have been substituted to study the substitution effects in a two-band superconductor and it's influence on the impurity scattering in and between σ and π bands. Mg_1-xAl_xB₂ and MgB_2-xC_x crystals were grown for x=0-0.3. Al and C dope MgB₂ with additional electrons, causing similar decrease of T_c. Li dopes MgB₂ with holes without significant decrease of T_c. Magnetic ion Mn²⁺ for Mg²⁺ leads to very rapid decrease of T_c. This indicates strong pair breaking by magnetic scattering centers. For Mn substituted crystals superconductivity is completely suppressed for x=0.02. Fe at low concentration up to x=0.03 is nonmagnetic impurity in MgB₂ therefore decreases T_c less rapidly than Mn. However, crystals with higher Fe concentration show rapid decrease of T_c, which indicates that Fe can be a magnetic impurity. Carbon substitution increases the upper critical field twice for x=0.05-0.10, while Al, Fe and Mn substitutions decrease this field. The upper critical field anisotropy γ decreases with all substitutions, but temperature dependence of γ is different, which indicates different scattering rates for different substitutions in π and σ bands. For Mn and Al, both energy gaps exist up to the highest substitution rate, while for C substitution, merging of two energy gaps was observed indicating influence of the interband scattering.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/8195 must be provided.

1. LnFeAsO single crystals grown at high pressure: influence of doping and substitutions on superconducting properties and structure
2. Field  dependence of the refrigerant capacity for La-based manganites
3. Rietveld refinement of TOF diffraction with multiple pulse overlap
4. Effect of Li-C and Li-Al codoping in MgB₂ single crystals
5. Single crystals of MgB₂: synthesis, substitutions and properties
6. Influence of pressure on magnetic properties of (Sr, La) (Ru, A)O₃ for A = Cr, Mn
7. Single crystals of pure and substituted MgB₂: crystal growth and physical properties
8. Al_xGa_1-xN bulk single crystals: Temperature dependence of Al solubility
9. The superconducting gaps of C-substituted and Al-substituted MgB2 single crystals by point-contact spectroscopy
10. Effect of preparation conditions on superconducting properties of (Bi,Pb)-Sr-Ca-Cu-O glass-ceramics