Characterization of localized hole states inPr1+xBa2−x

Abstract

We investigated the charge distribution in Pr1+xBa2−xCu3O6+y-crystals at liquid-He temperature by means of 63,65 Cu-and 141 Pr-NMR and NQR. The electric field gradients determined for the different oxygen coordinations of Cu(1) on the chains confirm the model that the hole states are localized in the O2pπ-orbitals of the CuO2-planes. The intensity and line-shape analysis of the Cu(1)-and Pr-resonances in the oxygen doping series (x ≈ 0, y = 0 . . . 1) and in the Pr/Ba solidsolution series (at y = 1) allows us to assign the Pr-resonance to Pr at RE-sites. Therefore, we can investigate the charge distribution in the CuO2-Pr-CuO2-layers by crystal field analysis of the Pr-signal. To consistently describe our results with neutron scattering data we propose that two Pr-states are present in the RE-layer, and ascribe them to Pr with and one without a hole localized in the oxygen coordination shell. NMR detects only the former, with a virtually nonmagnetic singlet ground state, while space-integral techniques are dominated by the latter, due to a quasi-doublet ground state and antiferromagnetism of its Pr-moments at low temperature.

Different self-consistent electronic structures ofPrBa2Cu3O7fromLSDAGhanbarian1 2008Phys. Rev. B11190View full textAdd to dashboardCite

“…It is basically inconsistent with the experimental observations. 29,37,38 It seems the U Cu overestimates the strong-correlation of Cu͑3d͒ electrons of Pr123 system and produces incorrect results. Thus, we have not used it here.…”

Praseodymium and oxygen role on magnetic properties of PrBa 2 Cu 3 O 6+ x

“…To explain this feature, one can invoke either some progressive change in the ordering of Cu(1) on chains [11]or a change of the magnetic structure of the Cu(2) in planes from collinear to non collinear, induced by the growing of the Pr moments. For this last explanation, a magnetic coupling between Pr and Cu(2) spins is needed, as argued by many authors in order to account for the high AF ordering of Pr [12,13]. …”

Superconducting Materials — A Topical Overview

“…This favors cation disorder with respect to the RE and Ba lattice sites [123] which leads to substantial T c degradation [124]. This disorder effect, oxygen deficiency and / or impurities had been suggested as reasons for the non-appearance of superconductivity in Pr-123 [125] and Tb-123 as the only non-SC members of the 123-HTS family. However, in 1998 first superconducting Pr-123 samples with T c~ 80 K [126] (105 K at 9.3 GPa [127]) could be synthesized which lost their SC properties within few days after their preparation.…”