Superconductivity in Impurity-Induced Tetragonal YBa2(Cu1-xFex)3O7-δ

Abstract
Lattice deformation and superconductivity in YBa2(Cu1-x Fe x )3O7-δ are studied in detail. An orthorhombic to tetragonal phase change is induced at x c≈0.02. A phase diagram in the temperature-concentration plane clarifies two regions of the tetragonal phase: one is, as known previously, induced mainly by the release of oxygen, and the other by the direct action of impurities. Bulk nature of superconductivity in the novel impurity-induced tetragonal phase is confirmed by magnetic susceptibility measurements.