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

摘要

Resonant soft x-ray Bragg diffraction at the Dy M4,5 edges has been exploitedto study Dy multipole motifs in DyB2C2. Our results are explained introducingthe intra-atomic quadrupolar interaction between the core 3d and valence 4fshell. This allows us to determine for the first time higher order multipolemoments 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-inof the orbitals at T_N has been observed, in contrast to earlier suggestions.The multipolar interaction and the structural transition cooperate along c butthey compete in the basal plane explaining the canted structure along [110].