Local tetragonal distortion in La_{0.7}Sr_{0.3}MnO_3 strained thin films probed by x-ray absorption spectroscopy

TL;DR

This study uses angular resolved X-ray Absorption Spectroscopy to investigate how tensile and compressive strains induce tetragonal distortions in La_{0.7}Sr_{0.3}MnO_3 thin films, affecting their structural and magnetic properties.

Contribution

It provides a quantitative model of strain-induced tetragonal distortion in La_{0.7}Sr_{0.3}MnO_3 thin films based on XANES and EXAFS analysis, highlighting the role of octahedral distortion over bond angles.

Findings

Tensile and compressive strains induce opposite tetragonal distortions.

Strain alters Mn-O bond lengths and Mn-Mn distances without changing Mn-O-Mn angles.

Octahedral distortion significantly influences the magnetic and transport properties.

Abstract

We report on an angular resolved X-ray Absorption Spectroscopy study of $La_{0.7}Sr_{0.3}MnO_{3}$ thin films epitaxially grown by pulsed laser deposition on slightly mismatched substrates which induce tensile or compressive strains. XANES spectra give evidence of tetragonal distortion within the $MnO_{6}$ octahedra, with opposite directions for tensile and compressive strains. Quantitative analysis has been done and a model of tetragonal distortion reflecting the strain has been established. EXAFS data collected in plane for tensile substrate confirm the change in the $Mn-O$ average bond distance and the increase of $Mn-Mn$ length matching with the enlargement of the cell parameter. From these results we conclude that there is no significant change in the $Mn-O-Mn$ angle. Our observations conflict with the scenarios which this angle is the main driving parameter in the sensitivity of manganite films properties to external strains and suggest that the distortion within the octahedra plays a key role in the modification of the transport and magnetic properties.