High-order Dy multipole motifs observed in DyB2C2 with resonant soft x-ray Bragg diffraction

TL;DR

This study uses resonant soft x-ray diffraction to identify and quantify high-order multipole moments in DyB2C2, revealing detailed charge density distributions and interactions that influence its magnetic structure.

Contribution

First direct determination of higher order multipole moments of Dy 4f electrons using resonant soft x-ray diffraction, elucidating their role in the material's charge density and magnetic structure.

Findings

Estimated Dy hexadecapole and hexacontatetrapole moments at -20% and +30% of quadrupolar moment.

No evidence of orbital lock-in at T_N, contrary to previous suggestions.

Multipolar interactions and structural transitions influence magnetic canted structure.

Abstract

Resonant soft x-ray Bragg diffraction at the Dy M4,5 edges has been exploited to study Dy multipole motifs in DyB2C2. Our results are explained introducing the intra-atomic quadrupolar interaction between the core 3d and valence 4f shell. This allows us to determine for the first time higher order multipole moments of dysprosium $4f$ electrons and to draw their precise charge density. The Dy hexadecapole and hexacontatetrapole moment have been estimated at -20% and +30% of the quadrupolar moment, respectively. No evidence for the lock-in of the orbitals at T_N has been observed, in contrast to earlier suggestions. The multipolar interaction and the structural transition cooperate along c but they compete in the basal plane explaining the canted structure along [110].