Transmission-electron-microscopy study of charge-stripe order in La(1.725)Sr(0.275)NiO(4)

TL;DR

This study uses transmission-electron microscopy to analyze charge stripe structures in La(1.725)Sr(0.275)NiO(4), revealing one-dimensional modulation, stripe centering preferences, and stacking frustrations, thus providing detailed local structural insights.

Contribution

It provides direct microscopic evidence of charge stripe configurations and their local variations, advancing understanding beyond previous diffraction-based studies.

Findings

Stripe modulation is one-dimensional within NiO2 planes.

Stripes tend to be either site-centered or bond-centered, with a bias towards site-centered.

Stripe spacing fluctuates, causing stacking frustration.

Abstract

We characterize the local structure and correlations of charge stripes in La(1.725)Sr(0.275)NiO(4) using transmission-electron microscopy. We present direct evidence that the stripe modulation is indeed one-dimensional within each NiO(2) plane. Furthermore, we show that individual stripes tend to be either site-centered or bond-centered, with a bias towards the former. The spacing between stripes often fluctuates about the mean, contributing to a certain degree of frustration of the approximate body-centered stacking along the c-axis. These results confirm ideas inferred from previous neutron-diffraction measurements on doped nickelates, and demonstrate that charge-stripe order is quite different from the conventional concept of charge-density-wave order.