Direct evidence for the suppression of charge stripes in epitaxial La$_{1.67}$Sr$_{0.33}$NiO$_4$ thin films

TL;DR

This study provides direct evidence that charge stripe order in epitaxial La$_{1.67}$Sr$_{0.33}$NiO$_4$ thin films is suppressed below a certain thickness, likely due to domain size reduction and phase transition from nematic to isotropic.

Contribution

It demonstrates the suppression of charge stripe order in thin films and links it to domain size effects and phase transition, using synchrotron x-ray diffraction and resistivity measurements.

Findings

Charge stripes are observed in thick films.

Stripe order disappears in films thinner than 2600 Å.

Suppression correlates with domain size reduction and phase transition.

Abstract

We have successfully grown epitaxial La$_{1.67}$Sr$_{0.33}$NiO$_4$ films with a small crystalline mosaic using pulsed laser deposition. With synchrotron radiation, the x-ray diffraction peaks associated with charge stripes have been successfully observed for relatively thick films. Anomalies due to the charge-ordering transition have been examined using four-point probe resistivity measurements. X-ray scattering provides direct evidence for suppression of the stripe phase in thin samples; the phase disappears for film thicknesses $\leqslant$ 2600 ~\AA{}. The suppression appears to be a result of shrinking the stripe phase domains. This may reflect the stripe phase progressing from nematic to isotropic.