Signature of an antiferromagnetic metallic ground state in heavily electron doped Sr2FeMoO6

TL;DR

This study demonstrates that heavily electron-doped Sr₂FeMoO₆ can exhibit an antiferromagnetic metallic ground state, supported by experimental evidence and theoretical calculations, revealing complex local structural phenomena.

Contribution

It provides the first experimental evidence of an antiferromagnetic metallic state in heavily doped Sr₂FeMoO₆ and uncovers unusual atomic-scale phase separation driven by La-O covalency.

Findings

Antiferromagnetic metallic state observed for x ≥ 1.4 in Sr₂₋ₓLaₓFeMoO₆.

Unusual atomic-scale phase separation involving La, Fe, Sr, and Mo regions.

Experimental results align with theoretical models considering local chemical fluctuations.

Abstract

Sr$_{2}$FeMoO$_6$ is a double perovskite compound, known for its high temperature behavior. Combining different magnetic and spectroscopic tools, we show that this compound can be driven to rare example of antiferromagnetic metallic state through heavy electron doping. Considering synthesis of Sr$_{2-x}$La$_x$FeMoO$_6$ (1.0 $\le{x}\le$ 1.5) compounds, we find compelling evidences of antiferromagnetic metallic ground state for $x\ge$1.4. The local structural study on these compounds reveal unusual atomic scale phase distribution in terms of La, Fe and Sr, Mo-rich regions driven by strong La-O covalency: a phenomenon hitherto undisclosed in double perovskites. The general trend of our findings are in agreement with theoretical calculations carried out on realistic structures with the above mentioned local chemical fluctuations, which reconfirms the relevance of the kinetic energy driven magnetic model.