Direct observation of oxygen superstructures in manganites

TL;DR

This study uses x-ray diffraction at the oxygen K-edge to directly observe oxygen superstructures in manganites, revealing orbital and charge orderings associated with oxygen 2p-states, and comparing findings with theoretical models.

Contribution

It provides direct experimental evidence of oxygen superstructures in manganites, clarifying the nature of oxygen orbital and charge orderings and testing theoretical predictions.

Findings

Oxygen orbital ordering in Bi0.31 Ca0.69 MnO3 with the same propagation vector as Mn orbitals

Absence of oxygen charge stripes at the observed periodicity in Bi0.31 Ca0.69 MnO3

Observation of 2p charge ordering in La7/8Sr1/8MnO3 with alternating hole-rich and hole-poor MnO planes

Abstract

We report the observation of superstructures associated with the oxygen 2p-states in two prototypical manganites using x-ray diffraction at the oxygen K-edge. We determine the nature of the orderings and discuss our picture with respect to novel theoretical models. In the stripe order system Bi0.31 Ca0.69 MnO3, hole-doped O states are found to be orbitally ordered, at the same propagation vector as the Mn orbital ordering, but no evidence is found to support a picture of oxygen charge stripes at this periodicity. In La 7/8 Sr 1/8 MnO3, we observe a 2p charge ordering described by alternating hole-poor and hole-rich MnO planes that is consistent with recent predictions.