Condensed Matter Physics Seminar
Current Challenges in the Investigation of Ruthenocuprates: A Progress Report
Professor Piotr W.
Northern Illinois University
The properties of superconducting RuSr2RECu2O8 (1212-type) and RuSr2RE2-yCeyCu2O10-δ RE=Gd, Eu (1222-type) ruthenocuprates attracted a lot of interest after the apparent coexistence of superconductivity (SC) and ferromagnetism (FM) was reported in these compounds. Whereas accommodating singlet state SC and FM in the same volume of the material echoes general considerations for mutually exclusive states, the HTSC-type crystal structure focuses attention on anisotropies of defining order parameters. The presence of magnetic order realized in the sublattice of the Ru ions could then be interesting also for extending our investigation of the superconducting state in cuprates. Before, however, satisfactory models can be considered, several experimental challenges remain. Detailed understanding of the magnetic state realized in the ruthenocuprates remains an open issue of fundamental importance. Status of this research will be discussed based on several experimental techniques involved. The defining role of the Cu->Ru substitution for increase of the superconducting Tc in Ru1-xSr2RECu2+xO8, as well as finding of the superconducting and non-superconducting phases of RuSr2RECu2O8 with no tracable difference in average stoichiometry raise tquestions for the presence of modifications in the local structure of the parent phase of the ruthenocpuprate. The effect of hole doping into the CuO2 planes (Ru->Cu, Ce->Gd substitutions), role of defects in the transition metal sublattices, as well as possible superstructure modifications will be briefly approached in discussion. Recent results extend the Cu->Ru substitution approach to the 1222-type of ruthenocuprates for which the new phases are also reported. The effort acknowledges support by the NSF (DMR-0105398) and Paul Scherrer Institute in Switzerland (muSR project RA-97-12)
Monday, December 8, 2003
Gant Science Complex
(The seminar is followed by coffee/tea, cookies, and an informal discussions.)