Synthesis and thermal stability of the solid solution AFeO2 (A = Ba, Sr, Ca)

Area of Science:

• Materials Science
• Solid-State Chemistry
• Magnetism

Background:

• Infinite layer iron oxides (AFeO(2)) with FeO(4) square-planar coordination are of interest for their unique properties.
• Understanding A-site substitution effects is crucial for tuning material characteristics.

Purpose of the Study:

• To investigate the impact of A-site substitution, specifically with alkali-earth elements, on the structural, thermal, and magnetic properties of AFeO(2).
• To determine the tolerance limit of Ba substitution in AFeO(2) and its effect on magnetic behavior and oxidation stability.

Main Methods:

• Synthesis and characterization of AFeO(2) with varying A-site substitutions.
• Analysis of structural, thermal, and magnetic properties through experimental techniques.
• Comparison of experimental results with first-principles calculations.

Main Results:

• Ba substitution is found to be tolerable up to 30% in AFeO(2), similar to ACuO(2) under high pressure.
• Ba substitution has a minimal impact on magnetic properties, contradicting theoretical predictions.
• Oxidation temperature and rate to the AFeO(2.5) phase are tunable by altering the out-of-plane distance.

Conclusions:

• A-site substitution, particularly with Ba, offers a pathway to tune the thermal properties of infinite layer iron oxides.
• The observed magnetic behavior under Ba substitution highlights discrepancies with theoretical models, necessitating further investigation.
• Control over the out-of-plane distance is a key factor in managing the oxidation stability of these materials.