Competing misfit relaxation mechanisms in epitaxial correlated oxides

TL;DR

This study investigates the complex strain relaxation mechanisms in epitaxial La0.7Sr0.3MnO3 thin films, revealing a hierarchical development of octahedral distortions that impact their electronic and magnetic properties.

Contribution

It provides the first experimental evidence of a four-stage hierarchical misfit relaxation process in correlated oxide thin films, linking electronic, elastic, and structural energy balances.

Findings

Identification of a four-stage hierarchical relaxation process.

Electronic softening causes interfacial dead layer formation.

Rigid octahedral tilts emerge later without affecting transport.

Abstract

Strain engineering of functional properties in epitaxial thin films of strongly correlated oxides exhibiting octahedral-framework structures is hindered by the lack of adequate misfit relaxation models. Here we present unreported experimental evidences of a four-stage hierarchical development of octahedral-framework perturbations resulting from a progressive imbalance between electronic, elastic and octahedral tilting energies in La0.7Sr0.3MnO3 epitaxial thin films grown on SrTiO3 substrates. Electronic softening of the Mn - O bonds near the substrate leads to the formation of an interfacial layer clamped to the substrate with strongly degraded magnetotransport properties, i.e. the so-called dead layer, while rigid octahedral tilts become relevant at advanced growth stages without significant effects on charge transport and magnetic ordering.