Effect of band-filling and structural distortions on the Curie temperature of Fe-Mo double perovkites

TL;DR

This study investigates how band-filling and structural distortions influence the Curie temperature in Fe-Mo double perovskites, revealing that electron filling enhances $T_C$ in La-substituted compounds, while structural factors also play a role.

Contribution

It provides detailed structural analysis correlating bond angles, bond distances, and Curie temperature variations with different A-site substitutions in Fe-Mo double perovskites.

Findings

Curie temperature increases with La substitution due to electron filling.

Bond angles are similar across series, but bond distances differ with La and Ca.

Structural distortions and electron filling jointly affect magnetic properties.

Abstract

By means of high resolution neutron powder diffraction at low temperature we have characterized the structural details of $\rm La_{x}Sr_{2-x}FeMoO_6$ ($0\leq {\rm x}\leq 0.5$) and $\rm Ca_{x}Sr_{2-x}FeMoO_6$ ($0\leq {\rm x}\leq 0.6$) series of compounds. This study reveals a similar variation of the mean bond-angle \FeOMo in both series. In contrast, the mean bond-distance \FeMoO\ increases with La but not with Ca substitution. Both series also present a different evolution of the Curie temperature ($T_C$), which raises in the La series and slightly decreases in the Ca one. We thus conclude that the enhancement of $T_C$ in the La series is due to the electron filling of the conduction band and a concomitant rising of the density of states at the Fermi level.