Observation of the novel type of ordering: Spontaneous ferriquadrupolar order

TL;DR

This paper reports the experimental observation of spontaneous ferriquadrupolar order in a rare-earth compound using spectroscopic techniques, supported by a mean field theoretical model explaining its emergence.

Contribution

It provides the first experimental evidence of ferriquadrupolar order and develops a mean field theory to explain this novel type of electronic ordering.

Findings

Ferriquadrupolar order observed in KDy(MoO4)2

Spectroscopic evidence of non-equivalent ion distortions

Theoretical model explaining the order's onset

Abstract

Using Raman and infrared spectroscopies the spontaneous ferriquadrupolar ordering has been observed in the rare-earth-based system KDy(MoO$_4$)$_2$. Ordered quadrupoles in the electron subsystem attend non-equivalent distortions of rare-earth ions in the ordered phase. The mean field theory explaining the onset of such a type of ordering has been constructed.