Electron Doping of a Double Perovskite Flat-band System

TL;DR

This study investigates how electron doping in Sr2FeSbO6 affects its electronic structure and magnetic properties, revealing a transition from antiferromagnetic to ferromagnetic coupling with doping.

Contribution

It provides experimental evidence of magnetic and structural changes in electron-doped Sr2FeSbO6, highlighting the role of flat bands and lattice geometry in magnetic behavior.

Findings

Magnetic susceptibility shows a maximum indicating antiferromagnetic interactions.

Doping induces a transition from antiferromagnetic to ferromagnetic coupling.

Structural analysis confirms doping levels and lattice stability.

Abstract

Electronic structure calculations indicate that the Sr2FeSbO6 double perovskite has a flat-band set just above the Fermi level that includes contributions from ordinary sub-bands with weak kinetic electron hopping plus a flat sub-band that can be attributed to the lattice geometry and orbital interference. To place the Fermi energy in that flat band, electron doped samples with formulas Sr2-xLaxFeSbO6 (0 < x < 0.3) were synthesized and their magnetism and ambient temperature crystal structures determined by high-resolution synchrotron X-ray powder diffraction. All materials appear to display an antiferromagnetic-like maximum in the magnetic susceptibility, but the dominant spin coupling evolves from antiferromagnetic to ferromagnetic on electron doping. Which of the three sub-bands or combinations is responsible for the behavior has not been determined.