Surface effects on the orbital order in the single layered manganite La0.5Sr1.5MnO4

TL;DR

This study reveals how the surface of a single-layered manganite exhibits rougher orbital order than the atomic surface, with temperature-dependent changes indicating a surface-induced phase transition.

Contribution

First observation of orbital truncation rods showing surface effects on orbital order in a layered manganite.

Findings

Orbital surface is significantly rougher than the atomic surface.

Surface exhibits a second order transition with temperature.

Orbital truncation rods reveal surface termination effects.

Abstract

We report the first observation of `orbital truncation rods' -- the scattering arising from the termination of bulk orbital order at the surface of a crystal. The x-ray measurements, performed on a cleaved, single-layered perovskite, La0.5Sr1.5MnO4, reveal that while the crystallographic surface is atomically smooth, the orbital `surface' is much rougher, with an r.m.s. deviation from the average `surface' of ~0.7nm. The temperature dependence of this scattering shows evidence of a surface-induced second order transition.