Weak charge-lattice coupling requires reinterpretation of stripes of charge order in La1-xCaxMnO3

TL;DR

This study reveals that in La1-xCaxMnO3, weak charge-lattice coupling challenges the traditional stripe model of charge order, suggesting a need to reinterpret the underlying mechanisms in manganites.

Contribution

The paper demonstrates that charge-lattice coupling in La1-xCaxMnO3 is too weak to produce stripe order, contradicting previous assumptions and prompting a reevaluation of charge ordering phenomena.

Findings

Electron diffraction shows absence of charge stacking faults.

Superlattice periodicity is uniform and not locked to the parent lattice.

Weak coupling implies charge localization is less likely due to lattice interactions.

Abstract

Modulations in manganites attributed to stripes of charge/orbital/spin order are thought to result from strong electron-lattice interactions that lock the superlattice and parent lattice periodicities. Surprisingly in La1-xCaxMnO3(x>0.5, 90 K), convergent beam (3.6 nm spot) electron diffraction patterns rule out charge stacking faults and indicate a superlattice with uniform periodicity. Moreover, large area electron diffraction peaks are sharper than simulations with stacking faults. Since the electron-lattice coupling does not lock the two periodicities (to yield stripes) it may be too weak to strongly localise charge.