Ferromagnetism in Chemically-synthesized Co-doped ZnO

Kumar, Shalendra; Kim, Y.J.; Koo, Bon Heun; Choi, Heekyu; Lee, C.G.; Sharma, S. K.; Knobel, M.; Gautam, Sanjeev; Chae, Kwang-Pyo

doi:10.3938/jkps.55.1060

Cited by 20 publications

(5 citation statements)

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“…According to previous works, the broad spectral features between 530 and 537 eV are assigned to the transition of O(1s) electrons to the hybridized orbitals of O(2p) and Zn(4s, 4p) states, while the sharp peak C is due to the transition of O(1s) electrons to more localized O 2p z and 2p x + y states . The O K-edge XAS does not show any feature related to the O(2p) and Zn(3d) hybridized orbitals, as expected for the Zn d 10 configuration in ZnO, appearing as sharp peaks in the low-energy region (labeled A in the figure) in 3d oxides. , …”

Section: Resultssupporting

confidence: 56%

“…26 The O Kedge XAS does not show any feature related to the O(2p) and Zn(3d) hybridized orbitals, as expected for the Zn d 10 configuration in ZnO, appearing as sharp peaks in the lowenergy region (labeled A in the figure) in 3d oxides. 26,27 Aiming to study how the modification of the local structural environment of oxygen verifies this assignment, we have performed a detailed ab initio calculation of the O K-edge XANES spectra by using the multiple-scattering program CONTINUUM, 28 included in the MXAN program package. 29 A complete discussion of the procedure can be found elsewhere.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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O K-Edge X-ray Absorption Spectroscopy in Al-Doped ZnO Materials: Structural vs Electronic Effects

Guglieri

Chaboy

2014

J. Phys. Chem. C

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This work reports an O K-edge X-ray absorption spectroscopy (XAS) study of Al-doped ZnO nanoparticles and films showing room-temperature ferromagnetism (RTFM). The origin of this ferromagnetism remains controversial as different conclusions are derived for analogous systems. Among those, charge-transfer effects and the presence of vacancies are often suggested, based on the modification of similar XAS spectra with respect to that of undoped ZnO. We present here a critical re-examination of the reported O K-edge absorption in these materials, by comparing the experimental spectra to ab initio theoretical calculations, paying special attention to the role of structural modifications, instead of the currently accepted electronic interpretation, into driving the observed spectral modifications. Our results indicate that the reported variations of the XAS spectral profile are not due to the charge-transfer effects involving Al and O, but are associated with the structural modification of the oxygen next-neighboring arrangement. Indeed, the structural changes are in agreement with the formation of interfaces between ZnO and alumina-based regions, upon the reaction between ZnO and Al. According to previous studies, the RTFM likely resides in these interfaces associated with the oxygen ions.

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Section: Resultssupporting

confidence: 56%

Section: ■ Results and Discussionmentioning

confidence: 99%

O K-Edge X-ray Absorption Spectroscopy in Al-Doped ZnO Materials: Structural vs Electronic Effects

Guglieri

Chaboy

2014

J. Phys. Chem. C

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“…In addition to the electrical and optical properties of undoped ZnO, the transition metal doped ZnO forms are promising candidate materials in the field of spintronics (spin-electronics). Various methods such as pulsed laser deposition [1], chemical vapor transport [2], electrodeposition [3], co-precipitation [4] and solid-state reaction [5], and spray pyrolysis [6] can be used to synthesize ZnO. Among these methods, spray pyrolysis technique can be applicable without vacuum environment; of course, this technique is cheap and displaying comparable properties and competitive functionality with that produced by other techniques.…”

Section: Introductionmentioning

confidence: 99%

Co doping induced structural and optical properties of sol–gel prepared ZnO thin films

Gungor

Güngör

Çalışkan

et al. 2014

Applied Surface Science

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The preparation conditions for Co doping process into the ZnO structure were studied by the ultrasonic spray pyrolysis technique. Structural and optical properties of the Co:ZnO thin films as a function of Co concentrations were examined. It was observed that hexagonal wurtzite structure of ZnO is dominant up to the critical value, and after the value, the cubic structural phase of the cobalt oxide appears in the X-ray diffraction patterns. Every band-edge of Co:ZnO films shifts to the lower energies and all are confirmed with the PL measurements. Co substitution in ZnO lattice has been proved by the optical transmittance measurement which is observed as the loss of transmission appearing in specific region due to Co 2+ characteristic transitions.

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“…Yongsheng Tan et al demonstrated that ferromagnetism is attributed to the intrinsic property of Eu-doped ZnO films and could be interpreted by the bound-magnetic-polaron (BMP) model[48]. Shalendra Kumar et al also explained the enhancement of ferromagnetism in ZnO:Co by BMP model[49].The magnetic exchange interaction between O vacancy and Dy 3+ ion aligns all the Dy 3+ ions around the O vacancy, forming BMPs. Once the overlapping of BMPs cross over the sample, ferromagnetic property is created which is consistent with our PL results which showed that there were large numbers of defects in Zn:Co:Dy:O nanoparticles.…”

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confidence: 96%

Influence of Co and Dy Doping on the Optical and Magnetic Properties of ZnO Nanoparticles for DMS Application

Thangeeswari

Murugasen

Velmurugan

2015

J Supercond Nov Magn

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Dysprosium-(Dy) and cobalt (Co)-doped zinc oxide (ZnO) nanoparticles with various concentrations have been synthesized by simple chemical precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDAX) measurements were conducted respectively for the structural, morphological, and compositional investigation of the sample. XRD analysis indicated that diffraction peaks of all the samples can be indexed to the hexagonal wurtzite structure of ZnO. No secondary phases including Co and Dy ions were detected in the samples even for the highest doping concentrations of Dy. Average particle size is found to be 25-34 nm. Scanning electron microscope and transmission electron microscope analysis revealed that the dopant atoms of Co and Dy are homogeneously distributed in ZnO wurtzite structure. The samples were characterized by EDAX to confirm the expected stoichiometry. In the photoluminescence spectra, Dy co-doped samples show a violet emission along with a broad yellow emission due to the 4 F 9/2 -6 H 15/2 inner shell transitions of Dy 3+ ion. The photoluminescence (PL) enhancement process in Dy co-doped ZnO:Co is mainly due to Dy as a sensibilizer which could effectively enhance the luminescence intensity. Absorption spectra of dysprosium-(Dy) and cobalt (Co)-doped ZnO nanoparticles exhibited enhanced optical absorption in visible region. Magnetization measurements have shown that the particles have room temperature ferromagnetic behavior with relatively high coercive fields which are decreasing with the increase of doping concentration. The analysis of optical and magnetic properties shows that Co-and Dy-doped ZnO nanoparticles are a promising material for DMS application and have potential applications in optoelectronic devices.

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Ferromagnetism in Chemically-synthesized Co-doped ZnO

Cited by 20 publications

References 0 publications

O K-Edge X-ray Absorption Spectroscopy in Al-Doped ZnO Materials: Structural vs Electronic Effects

O K-Edge X-ray Absorption Spectroscopy in Al-Doped ZnO Materials: Structural vs Electronic Effects

Co doping induced structural and optical properties of sol–gel prepared ZnO thin films

Influence of Co and Dy Doping on the Optical and Magnetic Properties of ZnO Nanoparticles for DMS Application

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