Abstract
The influence of transition metal substitutions (Ni, Fe, Co) and Zn at the Cu sites on T c and the oxygen isotope effect α o has been studied in the system La 2− y Sr y Cu 1− x M x O 4 with the optimum ( y = 0.15) and overdoped ( y = 0.20) compositions. Essential distinctions in the behavior of parameter α o for systems with heterovalent Fe and Co substitutions and isovalent Ni and Zn substitutions have been revealed. For Fe doped compounds with y = 0.15 the isotope effect was found to be very large: α o ≈ 1.3 at x = 0.011. The dependence of the isotope effect on the substituted atom concentration changes substantially when the degree of strontium doping varies. The experimental data were theoretically analyzed on the basis of the phonon mechanism of superconductivity and the concept of the existence of a singularity in the electron density of state N( E F). It is shown that the influence of paramagnetic impurities on the T c isotope shift of superconductors is enhanced when there is a sharp peak in N( E F). The difference in these effects for a system with the optimum strontium composition and for an overdoped system is also explained.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
