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

No abstract

No abstract

A long-standing issue about the Cu valency in selenospinel CuCr2Se4 was investigated by soft X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). Using the sensitivity of XAS and XMCD to the valence value of transition metal ion and its local symmetry, we checked the valence value of each cation in selenospinel CuCrxTi2−xSe4 (x = 1.0, 1.1, 1.5, and 2.0) and obtained spectroscopic evidence that a small amount of the Cu cation changes the valency from Cu(I) to Cu(II) as the Cr concentration increases from 1.0 to 2.0. Dependence of the Cu(II) concentration and the mean field magnetic exchange energy on the Cr concentration suggests the Cu d-hole could play a crucial role in the intriguing magnetic/electrical properties of CuCr2Se4.

The electronic and magnetic structures of Fe 1−x Cu x Cr 2 S 4 (0.1 x 0.5) spinel sulfides have been investigated systematically by performing photoemission spectroscopy (PES), soft x-ray absorption spectroscopy (XAS), and soft x-ray magnetic circular dichroism (XMCD) measurements using synchrotron radiation. Cr and Cu ions are found to be nearly trivalent (Cr 3+ ) and monovalent (Cu + ), respectively, and their valence states do not change with x. The Fe 2p XAS spectra of Fe 1−x Cu x Cr 2 S 4 are very similar to that of Fe metal, indicating that the Fe 3d electrons are strongly hybridized to other valence electrons. The Fe and Cr 2p XMCD spectra show that the magnetic moments of Cr ions and Fe ions are aligned antiparallel to each other and that both the Cr and Fe magnetic moments increase with increasing x. The valenceband PES study reveals that the Cr 3+ (t 3 2g ↓) 3d states are located at ∼1.5 eV below E F . The occupied Fe 3d states consist of the broad t 3 2g ↑ states, the e 2 g ↑ states at ∼4 eV below E F , and the e g ↓ states very close to E F . The filled Cu 3d 10 states lie at ∼2.5 eV below E F . This study suggests that the hybridized Fe e g ↓ and S 3p states near E F play an important role in determining the transport properties of Fe 1−x Cu x Cr 2 S 4 for x 0.5.