Nature of the low temperature ordering of Pr in PrBa_2Cu_3O_(6+x)

TL;DR

This paper presents a theoretical model explaining the low-temperature Pr ion ordering in PrBa_2Cu_3O_(6+x), highlighting the role of Cu-Pr coupling in the observed magnetic phenomena below 12-17 K.

Contribution

The model introduces a novel understanding of Pr ordering by considering multipole degrees of freedom and Cu-Pr coupling, explaining experimental neutron diffraction results.

Findings

Pr ions exhibit ab-plane dipole ordering below T_Pr.

Cu-Pr coupling significantly enhances Pr ordering temperature.

The model accounts for the anomalous magnetic behavior observed experimentally.

Abstract

Theoretical model is presented to describe the anomalous ordered phase of Pr ions in PrBa_2Cu_3O_(6+x) below T_Pr = 12-17 K. The model considers the Pr multipole degrees of freedom and coupling between the Cu and Pr subsystems. We identify the symmetry allowed coupling of Cu and Pr ions and conclude that only an ab-plane Pr dipole ordering can explain the Cu spin rotation observed at T_Pr by neutron diffraction by Boothroyd et al. [A. T. Boothroyd et al., Phys. Rev. Lett. 78, 130 (1997)]. A substantial enhancement of the Pr ordering temperature is shown to arise from the Cu-Pr coupling which is the key for the anomalous magnetic behavior in PrBa_2Cu_3O_(6+x).