Electronic structure of the cubic perovskiteSrMn1−xFexO3investigated by x-ray spectroscopies

Abstract

The electronic structures of SrMn 1−x Fe x O 3 ͑0 Յ x Յ 1͒ have been investigated by using photoemission spectroscopy ͑PES͒, soft x-ray absorption spectroscopy, and soft x-ray magnetic circular dichroism ͑XMCD͒. Both Mn and Fe ions are found to be nearly tetravalent for the whole range of x in SrMn 1−x Fe x O 3 . Valence-band PES measurements show the broader Fe 3d ͑t 2g 3 e g 1 ͒ bands than the Mn 3d ͑t 2g 3 ͒ bands and the finite metallic intensity near E F in the Fe 3d PES of SrFeO 3 in agreement with the metallic ground state of SrFeO 3 . The Fe 2p XMCD spectra exhibit the enhanced XMCD effect for 0.6Յ x Յ 0.8 in SrMn 1−x Fe x O 3 , which is consistent with the spin-glass behavior in the intermediate substitution, while the Mn 2p states exhibit the negligible XMCD effect.Perovskite SrFeO 3 shows the metallic behavior when fully oxygenated. 1,2 SrFeO 3 exhibits neither the Jahn-Teller distortion 3,4 nor the orbital ordering, 5 which is unusual considering that high-spin ͑HS͒ Fe 4+ ͑t 2g 3 e g 1 ͒ ions are usually Jahn-Teller active. Oxygen deficiency in SrFeO 3−␦ affects the transport properties dramatically, causing the metal-toinsulator transition ͑MIT͒ for ␦ Ն 0.15. 4,6-9 It is likely that

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“…However, the XAS spectra of Zn 0.974 Fe 0.026 O before and after O 2 annealing are different, indicating the different chemical states of Fe ion. Fe L 2 and L 3 edges of Zn 0.974 Fe 0.026 O films as deposited are located at ~708 eV and ~720 eV, respectively, and the line shape and L-edge peak position are coincident with those of Fe 2+ [133,134], indicating that Fe has a +2 oxidation state in Zn 0.974 Fe 0.026 O films. After O 2 annealing, the film shows a dominant peak near 710 eV, accompanied by double peaks near 721 and 723 eV, which are characteristic of Fe 3+ ion [135].…”

Photoemission spectroscopy study of metal-insulator transition inSrMn1−xFexO3

“…Fe 3d PES spectra exhibit a rather broad peak centered around ϳ2 eV BE and the weak emission near E F , which are identified as the occupied Fe t 2g 3 ↑ states and e g 1 ↑ states, respectively, since Fe ions are tetravalent ͑3d 4 ͒ in SrMn 1−x Fe x O 3 . 12 The broad feature around 6-7 eV in BE in both Mn 3d and Fe 3d PES are the O 2p-Mn/ Fe 3d hybridized states. The large O 2p electron character in Mn/ Fe 3d PES spectra suggests the strong hybridization between Mn/ Fe 3d and O 2p states in SrMn 1−x Fe x O 3 .…”

“…This trend agrees with that in the measured O 1s XAS spectra. 12 The O 2p states exhibit a large hybridization with Fe/ Mn 3d states, and the states between ϳ−4 and ϳ−8 eV are mainly due to the O 2p bands. Figure 5͑a͒ shows the combined Mn and Fe 3d PES spectra and the O 1s XAS spectra 18 of SrMnO 3 ͑x =0͒ and SrFeO 3 ͑x =1͒, respectively.…”

“…On the other hand, the analysis of x-ray photoemission spectra for isoelectronic CaFeO 3 suggested that the CO state results from the CD of ligand holes ͓2͑d 5 L គ ͒ → d 5 L គ 2 + d 5 ͔ rather than the CD of Fe-d electrons ͓2d 4 → d 3 + d 5 ͔ ͑L គ : an oxygen hole, or a ligand hole͒. [9][10][11] However, in our recent work based on soft x-ray absorption spectroscopy ͑XAS͒, 12 In this work, we have investigated the correlation between the electronic structures of SrMn 1−x Fe x O 3 and the MIT by using soft x-ray photoemission spectroscopy ͑PES͒ and soft…”

“…This Mn 2p 3/2 XAS reveals that Mn ions are formally tetravalent ͑3d 3 ͒ in SrMnO 3 , which was confirmed in our previous work. 12 It is well known that the 3d electron emissions of T ions are enhanced in T 2p → 3d RPES ͑Ref. 13͒ and that T 2p → 3d RPES has the advantage of being more bulk representative than T 3p → 3d RPES that occurs at lower h's.…”