X-ray absorption spectroscopy of transition-metal doped diluted magnetic semiconductors Zn1−xMxO

Okabayashi, Jun; Ono, Kanta; Mizuguchi, Masaki; Oshima, M.; Gupta, Subhra Sen; Sarma, D. D.; Mizokawa, T.; Fujimori, A.; Yuri, Masatada; Chen, C. T.; Fukumura, Tomoteru; Kawasaki, Masashi; Koinuma, Hideomi

doi:10.1063/1.1652248

Cited by 55 publications

(34 citation statements)

References 23 publications

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“…Energy positions and intensities of multiplet features are in good agreement with previous measure-ments of Zn 1−x Co x O ͑x = 0.011-0.054͒ and calculated Co 2p XAS spectra of a Co 2+ ion in a tetrahedral cluster ͑based on the configuration-interaction cluster model͒. 10,11 This suggests that the majority of Co dopants reside at the Zn sites ͑for all Co concentrations͒ and that they are tetrahedrally coordinated with the ligand O atoms. Therefore the magnetic properties of the samples investigated most likely arise from the hybridization between ligand O 2p orbitals and localized Co 3d orbitals in the substitutional sites.…”

Section: Methodssupporting

confidence: 87%

Effect of Co and O defects on the magnetism in Co-doped ZnO: Experiment and theory

Chang

Kurmaev

Boukhvalov³

et al. 2007

Phys. Rev. B

108

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The electronic structure of Zn 1−x Co x O ͑x = 0.02, 0.06, and 0.10͒ diluted magnetic semiconductors is investigated using soft x-ray emission spectroscopy and first-principles calculations. X-ray absorption and emission measurements reveal that most Co dopants are incorporated at the Zn sites and that free charge carriers are absent over a wide range of Co concentrations. The excess Co interstitials appear in the samples with high Co concentration ͑10 at. %͒ but are isolated without any direct exchange interaction with substitutional Co atoms. The lack of free charge carriers and the direct Co-Co interactions is responsible for the absence of ferromagnetism in the samples. First-principles calculations suggest that the exchange interaction between substitutional Co atoms induces only an antiferromagnetic coupling, and strong ferromagnetism in Co-doped ZnO requires not only free charge carriers but also the Co interstitials directly interacting with substitutional Co atoms.

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Section: Methodssupporting

confidence: 87%

Effect of Co and O defects on the magnetism in Co-doped ZnO: Experiment and theory

Chang

Kurmaev

Boukhvalov³

et al. 2007

Phys. Rev. B

108

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“…The properties were similar to the typical II-VI magnetic semiconductors [11,19]: the absorption due to d-d transition of Mn ion, the large magnetoresistance at low temperature, and the spin glass magnetic behavior. Figure 1 shows Photoemission spectroscopy revealed that Mn-doped ZnO had much larger p-d exchange constant [24], and X-ray absorption spectroscopy also confirmed the large p-d exchange constant for Mn-, Fe-, and Co-doped ZnO [25]. These results are consistent with their large MCD.…”

Section: Introductionsupporting

confidence: 78%

Magnetic Oxide Semiconductors

2006

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Magnetic oxide semiconductors, oxide semiconductors doped with transition metal elements, are one of the candidates for a high Curie temperature ferromagnetic semiconductor that is important to realize semiconductor spintronics at room temperature. We review in this paper recent progress of researches on various magnetic oxide semiconductors. The magnetization, magneto-optical effect, and magneto-transport such as anomalous Hall effect are examined from viewpoint of feasibility to evaluate the ferromagnetism. The ferromagnetism of Co-doped TiO 2 and transition metal-doped ZnO is discussed.

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“…The most important difference is that the overall amplitude of the exciton splitting is one order of magnitude smaller than the one expected for the value of the p-d exchange energy suggested by the Schrieffer-Wolf theory, 29,30 N 0 β = −3.1 ± 0.1 eV or implied by x-ray spectroscopy, N 0 β = −3.0 eV (Ref. 31). By a quantitative interpretation of the reflectivity spectra, it has been possible to find out how to link these puzzling results to a structure of the valence band in ZnO and to the strong p-d hybridization, expected for materials with the short anion-cation distance.…”

Section: Discussionmentioning

confidence: 97%

Influence ofs,p-dands−pexchange couplings on exc

et al. 2011

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This work presents results of near-band gap magnetooptical studies on Zn 1−x Mn x O epitaxial layers. We observe excitonic transitions in reflectivity and photoluminescence that shift toward higher energies when the Mn concentration increases and split nonlinearly under the magnetic field. Excitonic shifts are determined by the s,p−d exchange coupling to magnetic ions, by the electron-hole s−p exchange, and the spin-orbit interactions. A quantitative description of the magnetoreflectivity findings indicates that the free excitons A and B are associated with the 7 and 9 valence bands, respectively, the order reversed as compared to wurtzite GaN. Furthermore, our results show that the magnitude of the giant exciton splittings, specific to dilute magnetic semiconductors, is unusual: the magnetoreflectivity data are described by an effective exchange energy N 0 (β (app) − α (app) ) = +0.2 ± 0.1 eV, which points to small and positive N 0 β (app) . It is shown that both the increase of the gap with x and the small positive value of the exchange energy N 0 β (app) corroborate recent theory describing the exchange splitting of the valence band in a nonperturbative way, suitable for the case of a strong p−d hybridization.

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X-ray absorption spectroscopy of transition-metal doped diluted magnetic semiconductors Zn1−xMxO

Cited by 55 publications

References 23 publications

Effect of Co and O defects on the magnetism in Co-doped ZnO: Experiment and theory

Effect of Co and O defects on the magnetism in Co-doped ZnO: Experiment and theory

Magnetic Oxide Semiconductors

Influence ofs,p-dands−pexchange couplings on exc

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