X-ray spectroscopic study of BaFeO${}_3$ thin films; an Fe${}^{4+}$ ferromagnetic insulator

Abstract

We investigated the electronic and magnetic properties of fully oxidized BaFeO3 thin films, which show ferromagnetic-insulating properties with cubic crystal structure, by hard x-ray photoemission spectroscopy (HAXPES), x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD). We analyzed the results with configuration-interaction (CI) cluster-model calculations for Fe4+, which showed good agreement with the experimental results. We also studied SrFeO3 thin films, which have an Fe4+ ion helical magnetism in cubic crystal structure, but are metallic at all temperatures. We found that BaFeO3 thin films are insulating with large magnetization (2.1muB/formula unit) under ~ 1 T, using valence-band HAXPES and Fe 2p XMCD, which is consistent with the previously reported resistivity and magnetization measurements. Although Fe 2p core-level HAXPES and Fe 2p XAS spectra of BaFeO3 and SrFeO3 thin films are quite similar, we compared the insulating BaFeO3 to metallic SrFeO3 thin films with valence-band HAXPES. The CI cluster-model analysis indicates that the ground state of BaFeO3 is dominated by d5L (L: ligand hole) configuration due to the negative charge transfer energy, and that the band gap has significant O 2p character. We revealed that the differences of the electronic and magnetic properties between BaFeO3 and SrFeO3 arise from the differences in their lattice constants, through affecting the strength of hybridization and bandwidth.

arXiv comment8 pages, 5 figures

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Cited by in corpus (8)

• Electronic structure of negative charge transfer CaFeO3 across the metal-insulator transition
• Orbital engineering in nickelate heterostructures driven by anisotropic oxygen hybridization rather than orbital energy levels
• Topological Properties and Functionalities in Oxide Thin Films and Interfaces
• Anomalous charge and negative-charge-transfer insulating state in cuprate chain-compound KCuO_2
• Photoinduced demagnetization and insulator-to-metal transition in ferromagnetic insulating BaFeO${}_3$ thin films
• Itinerancy-dependent non-collinear spin textures in SrFeO3, CaFeO3, and CaFeO3/SrFeO3 heterostructures probed via resonant x-ray scattering
• Impact of oxygen doping and oxidation state of iron on the electronic and magnetic properties of BaFeO$_{3-δ}
• Negative charge transfer energy in correlated compounds