Studies on the Paramagnetic Impurity Y2BaCuO5 in Superconducting YBa2Cu3O7-￥? Phase

摘要

Conventional ceramic method has been used to prepare the green phase, Y2BaCuO5, commonly observed in 90-K superconductor YBa2Cu3O7-ヤ as an impurity phase. The powder X-ray diffraction analysis indicates that Y2BaCuO5 has an orthorhombic symmetry with lattice parameter of a = 12.2 ∈, b = 5.61 ∈, and c = 7.14 ∈. The average g-value 2.13 observed in ESR spectrum is attributable to Cu2+ stabilized in C4v field. From the magnetic susceptibility (レeff = 2.29 BM) and the ESR measurements, it is confirmed that Cu(ケ) 3d9 electrons in Y2BaCuO5 are localized and can be characterized by Curie-Weiss behavior. Optical reflectance spectrum shows a broad absorption peak around 680 nm due to dxy ℃ dx2-y2 eletronic transition.