Proximity to an orbital order with charge disorder state in optimally-doped \textit{RE}\textsubscript{5/8}Ca\textsubscript{3/8}MnO\textsubscript{3} perovskites

TL;DR

This study investigates how lattice strain and octahedral rotations influence charge and orbital ordering in optimally-doped RECaMnO perovskites, revealing proximity to a novel charge-disordered orbital order linked to colossal magnetoresistance.

Contribution

It uncovers the relationship between lattice distortions and ordering phenomena, identifying a nearby orbital order state that competes with ferromagnetic metallicity in these materials.

Findings

Lattice strain states are close to a charge-disordered orbital order.

This order competes with the ferromagnetic metallic phase.

Strain effects influence charge and orbital ordering in manganites.

Abstract

The evolution of charge and orbital ordering phenomena in optimally-doped \textit{RE}\textsubscript{5/8}Ca\textsubscript{3/8}MnO\textsubscript{3} (RECMO, \textit{RE} $=$ rare-earth) manganite perovskites has been investigated through average structure synchrotron x-ray and neutron powder diffraction techniques. We demonstrate the intricate relationship between the \textit{B}O\textsubscript{6} octahedral rotation magnitude and lattice strain distortions acting in this series and how they tune macroscopic signatures describing ordering behavior. Through careful symmetry-motivated crystallographic analysis, we show that for the range of RECMO compositions which famously contain maxima in the colossal magnetoresistance (CMR) response, their lattice strain states are in close proximity to that associated with a novel orbital order:charge disordered state we have recently unveiled in the quadruple manganite perovskites Na\textsubscript{1-\textit{x}}Ca\textsubscript{\textit{x}}Mn\textsubscript{7}O\textsubscript{12}. We establish that this order is the primary state which competes with the ferromagnetic metallic state which ultimately leads to phase coexistence and the emergence of CMR. Our results lend themselves to aiding a further understanding of how particular chemical complexities can control charge and orbital ordering phenomena, and also the general properties of manganite perovskites and other related systems \textit{via} strain effects.