Magnetism, Superconductivity, and Chemical Substitutions in YBa2Cu3O7-δ

摘要: Twelve compounds with the formula RBa2Cu3O7-δ where δ≍0.1 and R=Y or a lanthanide element except Ce, Pm, Tb, crystallize in same layered orthorhombic perovskite-like structure (see article by I.K. Schuller J.D. Jorgensen this issue). All such are superconducting transition temperatures Tc≍92-94 K, for R=Pr. The compound PrBa2Cu3O7-δ appears to be special case, since it does not exhibit metallic behavior is superconducting. Historically, prototype YBa2Cu3O7-δ singularly important was first material Tc greater than 77 boiling point of liquid nitrogen. In meantime, yet higher Tc's have been obtained at very high pressure (Tc˜107 K 150 kbar)5 new Bi-Sr-Ca-Cu-O (maximum Tc≍110 K)6 Tl-Ba-Ca-Cu-O Tc≍125 K)7 systems A.W. Sleight, M.A. Subramanian, C.C. Torardi issue).The origin nature superconductivity compounds, other copper oxide as well, presently understood constitute formidable challenge experimentalists theorists alike. One most intriguing possibilities that magnetic mechanism, rather electronphonon interaction, responsible formation electron pairs oxides. primary evidence pairing mechanism proximity antiferromagnetism concentration holes conducting CuO2 planes varied,8 discussed below compounds.