Resonant X-ray scattering investigation of the multipolar ordering in Ca3Co2O6

TL;DR

This study uses resonant x-ray scattering to investigate multipolar ordering in Ca3Co2O6, revealing a method to distinguish parity even and odd tensor contributions in a centrosymmetric system.

Contribution

It demonstrates the experimental separation of parity even and odd multipolar contributions in Ca3Co2O6 using RXS, advancing understanding of multipolar order detection.

Findings

New weak reflections observed at magnetic propagation vector

Successful separation of parity even and odd tensor contributions

Potential for observing isolated multipoles in centrosymmetric systems

Abstract

We have performed a resonant x-ray scattering (RXS) study near the Co K edge on a single crystal of Ca3Co2O6. In the magnetically ordered phase a new class of weak reflections appears at the magnetic propagation vector tau (1/3,1/3,1/3). These new reflections allow direct access to the dipolar-quadrupolar E1E2 scattering channel. The theoretical possibility of observing isolated E1E2 electromagnetic multipoles has attracted a lot of interest in the recent years. Unfortunately in many system of interest, parity even and parity odd tensor contributions occur at the same positions in reciprocal space. We demonstrate that in Ca3Co2O6 it is possible to completely separate the parity even from the parity odd terms. The possibility of observing such terms even in globally centrosymmetric systems using RXS has been investigated theoretically; Ca3Co2O6 allows a symmetry based separation of this contribution.