The Pr L 3-edge x-ray absorption near edge structure spectra and antiferromagnetic T N(Pr) data for the parent system PrBa 2Cu 3O 7-y (0≤y<1) and the oxygenated system Pr 1+xBa 2-xCu 3O 7-y (0≤x≤1;-0.27≤y≤0.05) are reported. The formal Pr valence in the PrO 8 cage decreases from 3.18 for PrBa 2Cu 3O 6.95 [T N(Pr)=18.5 K], to 3.12 for Pr 1.2Ba 1.8Cu 3O 6.98 (15.5 K), 3.03 for Pr 1.6Ba 1.4Cu 3O 7.16 (8 K), and 3.00 for Pr 2BaCu 3O 7.27 [T N(Pr) not observed]. The Pr valence depends both on the number of holes available in the PrO 8 cage and the Pr 4f-O 2p π hybridization strength. On the other hand, anomalous T N(Pr) is a direct result of exchange interaction though Pr-O-Pr hybridization. However, the relative contribution from Pr IV-Pr IV superexchange via strong Pr-O orbital hybridization and Pr III-Pr III/Pr III-Pr IV superexchange paths is unclear.
ASJC Scopus subject areas
- Physics and Astronomy(all)