On the Superconductivity Suppression in Eu(1)(−)(x)Pr(x)Ba(2)Cu(3)O(7)(−)(δ)

This article reports on the non-trivial suppression of superconductivity in the Eu(1−x)Pr(x)BCO cuprates. As non-magnetic Eu(3+) ions are replaced by Pr(3+) carrying a magnetic moment, spin-related superconductivity loss can be expected. The research shows that the superconductivity disappearance for x > 0.4 results from depletion of the carriers and their localization. The above conclusion was drawn by low-temperature X-ray diffraction analysis showing increased characteristic phonon frequencies with Pr content. This mechanism should promote electron–phonon coupling, at least for acoustic phonons. However, the inverse phenomenon was detected. Namely, there is a gradual deterioration of the optical phonons responsible for vibration of the Cu–O bonds with Pr increasing, as evidenced by Raman spectroscopy. Furthermore, the results of X-ray absorption spectroscopy precisely showed the location of the carriers for Pr-rich specimens. Finally, a schematic diagram for Eu(1−x)Pr(x)BCO is proposed to consolidate the presented research.