On the influence of magnetic and nonmagnetic impurities on the properties of yttrium-based high-Tc superconductors

Abstract

The influence of impurities on the physical properties of YBa2Cu3O7−δ superconducting ceramics is investigated. Samples of yttrium ceramics with different Ni, Zn, Co, Fe, and Ga impurity contents were prepared for this study, and the superconducting fraction, the low-frequency susceptibility in an external dc field, and the temperature dependence of the magnetic susceptibility in a weak ac field were measured for each sample. The last of these measurements permits a more precise determination of the critical temperature (the start of the transition) without regard for percolation effects. The experimental results show a stronger suppression of the superconducting state by nonmagnetic impurities, thus confirming the presence of d-state pairs in these superconductors. The degree of suppression of superconductivity by magnetic impurities depends on the preference of the impurities to locate in Cu(1) or Cu(2) sites.

Scattering Due to Non-magnetic Disorder in 2D Anisotropic d-wave High T<sub>c</sub> Superconductors

“…In particular, to this work, the first experiments investigating the influence of transition metal impurities in HTSCs, showed that nonmagnetic disorder suppress superconductivity, more strongly than magnetic impurities disorder [16,24,37], on the contrary to BCS superconductors, where only magnetic impurities reduce the transition temperature (T C ).…”

“…The superconducting gap for this symmetry has lines nodes on the Fermi surface corresponding to the one-dimensional irreducible representation B1g of the tetragonal point symmetry group D4h (Tsuei and Kirtley 2000). In a 𝑑 𝑥 2 −𝑦 2 symmetry gap, nonmagnetic disorder strongly quenches superconducting ordering leading to strong suppression of Tc (Sanikidze et al 2005).…”