Curie temperature enhancement of electron doped Sr$_2$FeMoO$_6$ perovskites studied by photoemission spectroscopy

TL;DR

This study investigates how electron doping via La substitution affects the electronic structure and Curie temperature of Sr$_2$FeMoO$_6$ perovskites, revealing increased density of states at the Fermi level and insights into ferromagnetism.

Contribution

It provides detailed photoemission spectroscopy analysis of electron-doped Sr$_2$FeMoO$_6$, highlighting the role of Mo-derived states in ferromagnetism enhancement.

Findings

Density of states at E$_F$ increases with La doping.

Electron doping mainly enhances Mo-derived states.

Insights into the origin of ferromagnetism in doped oxides.

Abstract

We report here on the electronic structure of electron-doped half-metallic ferromagnetic perovskites such Sr$_{2-x}$La$_x$FeMoO$_6$ ($x$=0-0.6) as obtained from high-resolved valence-band photoemission spectroscopy (PES). By comparing the PES spectra with band structure calculations, a distinctive peak at the Fermi level (E$_F$) with predominantly (Fe+Mo) t$_{2g}^\downarrow$ character has been evidenced for all samples, irrespectively of the $x$ values investigated. Moreover, we show that the electron doping due to the La substitution provides selectively delocalized carriers to the t$_{2g}^\downarrow$ metallic spin channel. Consequently, a gradual rising of the density of states at the E$_F$ has been observed as a function of the La doping. By changing the incoming photon energy we have shown that electron doping mainly rises the density of states of Mo parentage. These findings provide fundamental clues for understanding the origin of ferromagnetism in these oxides and shall be of relevance for tailoring oxides having still higher T$_C$.