Ce-doping and reduction annealing effects on electronic states in Pr\(_{2-x}\)Ce\(_{x}\)CuO\(_4\) studied by Cu \({K}\)-edge X-ray absorption spectroscopy

• Published in: arXiv.org 2018-07
• Main Authors: Asano, Shun, Ishii, Kenji, Matsumura, Daiju, Tsuji, Takuya, Toshiaki Ina, Suzuki, Kensuke M, Fujita, Masaki
• Format: Article
• Language: English
• Subjects: Annealing; Copper; Copper oxides; Doping; Electron states; Electrons; Oxygen ions; Reduction; Spectrum analysis; Substitutes; Toxicity; X ray absorption
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1804.10891

We investigated Ce-substitution and reduction annealing effects on the electronic states at copper sites by Cu \({K}\)-edge x-ray absorption near-edge structure measurements in Pr\(_{2-x}\)Ce\(_x\)CuO\(_{4+\alpha-\delta}\) (PCCO) with varying \(x\) and \(\delta\) (the amount of oxygen loss during annealing) values. Absorption near-edge spectra were modified by Ce-substitution and reduction annealing in a similar manner with increasing \(x\) and \(\delta\). Considering electron doping by Ce-substitution, this similarity indicates an increase of electron number at the copper sites due to annealing \(n_{\rm AN}\). Thus, the total number of electrons is determined by the amount of Ce and oxygen ions. Furthermore, quantitative analyses of the spectra clarified that the number of Cu\(^+\) sites, corresponding to the induced electron number by Ce-substitution \(n_{\rm Ce}\) increases linearly with \(x\) in the as-sintered PCCO (\(\delta=0\)), whereas \(n_{\rm AN}\) is not exactly equal to twice of \(\delta\), which is expected from charge neutrality. For each \(x\)-fixed sample, \(n_{\rm AN}\) tends to exceed 2\(\delta\) with increasing \(\delta\), suggesting the emergence of two types of carrier due to annealing.