Electron doping of a double-perovskite flat-band system

Electronic structure calculations indicate that the Sr2FeSbO6 double perovskite has a flat -band set just above the Fermi level that includes contributions from ordinary subbands with weak kinetic electron hopping plus a flat subband 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 & LE; x & LE; 0.3) were synthesized, and their magnetism and ambient temperature crystal structures were 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 subbands or combinations is responsible for the behavior has not been determined.

Automated summary

Electronic structure calculations show that Sr2FeSbO6 double perovskite has a flat-band set just above the Fermi level, which includes contributions from ordinary subbands with weak kinetic electron hopping and a flat subband attributed to lattice geometry and orbital interference. Electron-doped Sr2-xLaxFeSbO6 samples (0 ≤ x ≤ 0.3) were synthesized to place the Fermi energy in that flat band, and their magnetism and crystal structures were analyzed. The dominant spin coupling changes from antiferromagnetic to ferromagnetic upon electron doping, but it remains unclear which subband or combination is responsible for this behavior.