On the Superconductivity Suppression in Eu1-xPrxBa2Cu3O7-δ.

This article reports on the non-trivial suppression of superconductivity in the Eu1-xPrxBCO cuprates. As non-magnetic Eu3+ ions are replaced by Pr3+ 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 Eu1-xPrxBCO is proposed to consolidate the presented research.