Reduction Annealing Effects on Electronic States in T’-structured Cuprate Superconductor

Abstract

In this article, we introduce recent studies of reduction annealing effects on physical properties in T’-structured cuprate oxide using quantum beam spectroscopy. Our Cu K-edge x-ray absorption near-edge structure (XANES) study on the electronic states of T’-structured Pr_2-xCe_xCuO_4+α-δ clearly shows increase of number of electron at the copper sites due to annealing, similar to the case of Ce substitution. The qualitative analyses, furthermore, suggest the emergence of holes as well as electrons in the heavily Ce-doped Pr_2-xCe_xCuO_4+α-δ due to annealing. The role of annealing procedure, which is necessary for the appearance of superconductivity in T’-structured cuprates, is discussed in connection with recent photoemission spectroscopy and muon spin relaxation/rotation studies.