Novel Orbital Ordering induced by Anisotropic Stress in a Manganite Thin Film

TL;DR

This study reveals how anisotropic stress in a manganite thin film induces novel orbital ordering, with phase transitions characterized by x-ray diffraction, highlighting substrate-induced anisotropy as a new control parameter.

Contribution

It demonstrates that substrate anisotropy can induce and control new orbital orderings in manganite thin films, a novel approach for phase manipulation.

Findings

Lattice parameters change drastically at the metal-insulator transition.

Superlattice reflections appear below 140K indicating orbital ordering.

Anisotropic stress from the substrate influences phase transitions and orbital structures.

Abstract

We performed resonant and nonresonant x-ray diffraction studies of a Nd0.5Sr0.5MnO3 thin film that exhibits a clear first-order transition. Lattice parameters vary drastically at the metal-insulator transition at 170K (=T_MI), and superlattice reflections appear below 140K (=T_CO). The electronic structure between T_MI and T_CO is identified as A-type antiferromagnetic with the d_{x2-y2} ferroorbital ordering. Below T_CO, a new type of antiferroorbital ordering emerges. The accommodation of the large lattice distortion at the first-order phase transition and the appearance of the novel orbital ordering are brought about by the anisotropy in the substrate, a new parameter for the phase control.