Bulk-sensitive photoemission spectroscopy of A(2)FeMoO(6) double perovskites (A = Sr, Ba)

The electronic structures of ${\mathrm{Sr}}_{2}{\mathrm{FeMoO}}_{6}$ (SFMO) and ${\mathrm{Ba}}_{2}{\mathrm{FeMoO}}_{6}$ (BFMO) double perovskites have been investigated using Fe $2\stackrel{\ensuremath{\rightarrow}}{p}3d$ resonant photoemission spectroscopy (PES) and the Cooper minimum in the Mo $4d$ photoionization cross section. The states close to the Fermi level are found to have a strongly mixed Mo\char21{}Fe ${t}_{2g}$ character, indicating that the Fe valence is far from pure $3+.$ The Fe ${2p}_{3/2}$ x-ray absorption spectroscopy spectra reveal the mixed-valent ${\mathrm{Fe}}^{3+}\char21{}{\mathrm{Fe}}^{2+}$ configurations, and a larger ${\mathrm{Fe}}^{2+}$ component for BFMO than for SFMO, suggesting an operative double exchange interaction. The valence-band PES spectra reveal good agreement with the local-spin-density-approximation $(\mathrm{LSDA})+U$ calculation.