Evolution of Superconducting Properties of LiFeAs Single Crystals Doped with Magnetic or Nonmagnetic Impurities

• Published in: Journal of superconductivity and novel magnetism 2013-04, Vol.26 (4), p.1189-1193
• Main Authors: Shlyk, L., Bischoff, M., Rose, E., Niewa, R.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Critical current density; Critical currents; Cross-disciplinary physics: materials science; rheology; Crystal structure; Exact sciences and technology; Flux pinning; Impurities; Magnetic Materials; Magnetic relaxation; Magnetism; Materials science; Original Paper; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Physics and Astronomy; Pinning; Properties of type I and type II superconductors; Single crystals; Strongly Correlated Systems; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Superconductivity; Vortex lattices ,flux pinning, flux creep
• ISSN: 1557-1939; 1557-1947
• DOI: 10.1007/s10948-012-1980-8

The effect of magnetic Co 2+ and nonmagnetic Ga 3+ impurities on the crystal structure and superconducting properties of LiFeAs single crystals has been investigated. A large T c decrease of about 4.8 K/at% is observed in Ga-doped LiFeAs. This rate is higher than that of the material doped with magnetic Co impurities (∼3.7 K/at%). The greater T c suppression in the Ga case is likely due to the pair breaking associated with the significant changes in the crystal structure of the doped material. The increase of the critical current densities in intermediate magnetic fields ( H ⊥  ab ) indicates that a very small amount of Ga (0.5 at%) acts as an effective pinning site for flux pinning enhancement in the material. The analysis of the temperature and field dependencies of the magnetic relaxation is consistent with the collective pinning model for the Co-doped material, while the magnetic relaxation measurements combined with the peak position of the critical current density in the B – T phase diagram of Ga-doped LiFeAs suggest an elastic–plastic transition of the vortex lattice at higher temperatures and fields.