Local Structure and It's Effect on The Ferromagnetic Properties of La$_{0.5}$Sr$_{0.5}$CoO$_3$ thin films}

TL;DR

This study investigates how local structural distortions in strained La$_{0.5}$Sr$_{0.5}$CoO$_3$ thin films influence their ferromagnetic properties, revealing that bond length changes significantly affect the Curie temperature.

Contribution

The paper provides detailed measurements of local structure under strain and highlights the limitations of the double exchange model in predicting magnetic changes.

Findings

Lattice mismatch strain alters bond lengths and angles.

Bond length changes have a major impact on bandwidth.

Double exchange model underestimates the effect on Curie temperature.

Abstract

We have used high-resolution Extended X-ray Absorption Fine-Structure and diffraction techniques to measure the local structure of strained La$_{0.5}$Sr$_{0.5}$CoO$_3$ films under compression and tension. The lattice mismatch strain in these compounds affects both the bond lengths and the bond angles, though the larger effect on the bandwidth is due to the bond length changes. The popular double exchange model for ferromagnetism in these compounds provides a correct qualitative description of the changes in Curie temperature $T_C$, but quantitatively underestimates the changes. A microscopic model for ferromagnetism that provides a much stronger dependence on the structural distortions is needed.