Electronic structure of the charge disproportionate and metallicity in LaFe1-xMoxO3 studied by resonant x-ray spectroscopies

• A metal-insulator transition and its intriguing properties were recently reported based on doping of the antiferromagnetic insulator LaFeO3. Through doping at the B site by Mo to the insulating perovskite LaFeO3 exhibits a coexistence of an antiferromagnetic ordering with room-temperature metallicity at higher doping levels, an unusual ground state for an oxide perovskite. Replacing Fe by Mo in the Fe-O6 octahedra enhances the separation of the two 2 Fe-O bonds relative to the orthorhombic LaFeO3, largely retaining the centrosymmetric character of the Fe sites, as confirmed through extended x-ray absorption fine structure. Mo ions appear to be homogeneously doped, with average valency of both metal sites monotonically decreasing with increasing Mo concentration. Resonant photoemission was recorded for both Fe and Mo to obtain element specific spectral information on the projected 3d and 4d partial density of states. The data shows gradual increase of spectral weight at the Fermi level that is attributed to Mo d states, while the Fe d states primarily reside at higher binding energy in the valence band, with significant hybridization with O 2p states. The RIXS spectra show strong electron correlation effects from d-d inelastic features and broad charge-transfer excitations for x = 0.2 where the compound becomes metallic. This is in contrast to the insulating parent LaFeO3 compound and insulating samples with lower Mo content. The coexistence of both bound and continuum excitations observed in the RIXS spectra provides strong evidence for charge disproportionation with features that are linked to the disproportionate Fe sites.

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NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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Physics with spec. in Atomic, Molecular and Condensed Matter Physics

Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik

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