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We report on the results of x-ray absorption (XAS), x-ray magnetic circular dichroism (XMCD), and photoemission experiments on n-type Zn1−xCoxO (x = 0.05) thin film, which shows ferromagnetism at room temperature. The XMCD spectra show a multiplet structure, characteristic of the Co 2+ ion tetrahedrally coordinated by oxygen, suggesting that the ferromagnetism comes from Co ions substituting the Zn site in ZnO. The magnetic field and temperature dependences of the XMCD spectra imply that the non-ferromagnetic Co ions are strongly coupled antiferromagnetically with each other.

We have studied the electronic structure of the diluted magnetic semiconductor Ga 1−x Mn x N ͑x = 0.0, 0.02, and 0.042͒ grown on Sn-doped n-type GaN using photoemission and soft x-ray absorption spectroscopy. Mn L-edge x-ray absorption have indicated that the Mn ions are in the tetrahedral crystal field and that their valence is divalent. Upon Mn doping into GaN, new states were found to form within the band gap of GaN, and the Fermi level was shifted downward. Satellite structures in the Mn 2p core level and the Mn 3d partial density of states were analyzed using configuration-interaction calculation on a MnN 4 cluster model. The deduced electronic structure parameters reveal that the p-d exchange coupling in Ga 1−x Mn x N is stronger than that in Ga 1−x Mn x As.

The electronic structures of the antiferromagnetic semiconductor FeS and ferrimagnetic metals Fe 7 S 8 and Fe 7 Se 8 have been studied by spin-integrated and spin-resolved photoemission spectroscopy and inversephotoemission spectroscopy. The overall Fe 3d bandwidth in the photoemission spectra is 25-30 % narrower than the density of states ͑DOS͒ predicted by first-principles band-structure calculations and is accompanied by an intense tail on the high-binding-energy side, indicating the correlated nature of electrons in the Fe 3d band. Deviation from the band DOS is more significant in Fe 7 S 8 than in Fe 7 Se 8 , and in the minority-spin spectra than in the majority-spin spectra. Cluster-model calculation for FeS has shown satellite structures at high binding energies, but the calculated spectral line shape is not in good agreement with experiment compared to the band DOS. By introducing a self-energy correction to the band DOS, we could explain the narrowing of the overall Fe 3d bandwidth and the high-binding-energy tail shape but not for the unusual broadening of the Fe 3d band within ϳ1 eV of the Fermi level. ͓S0163-1829͑98͒02415-1͔