Magnetism of Co-doped ZnO epitaxially grown on a ZnO substrate

In order to unravel the magnetism of Co-doped ZnO films, we have performed rigorous experiments on Co-doped ZnO grown on O-polar ZnO (0001) substrates by molecular beam epitaxy. We find that the ZnO:Co with Co composition less than 20% is paramagnetic even at low temperatures, whereas that with Co c...

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Bibliographic Details
Published in:Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2012-05, Vol.85 (17), Article 174430
Main Authors: Li, Li, Guo, Y., Cui, X. Y., Zheng, Rongkun, Ohtani, K., Kong, C., Ceguerra, A. V., Moody, M. P., Ye, J. D., Tan, H. H., Jagadish, C., Liu, Hui, Stampfl, C., Ohno, H., Ringer, S. P., Matsukura, F.
Format: Article
Language:English
Subjects:
Condensed matter
Epitaxial growth
Ferromagnetism
Magnetism
Mathematical analysis
Origins
Three dimensional
Zinc oxide
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Summary:In order to unravel the magnetism of Co-doped ZnO films, we have performed rigorous experiments on Co-doped ZnO grown on O-polar ZnO (0001) substrates by molecular beam epitaxy. We find that the ZnO:Co with Co composition less than 20% is paramagnetic even at low temperatures, whereas that with Co composition of 20% shows ferromagnetism at room temperature. Although an additional n-type doping with Ga increases the magnitude of magnetization, the origin of the observed ferromagnetism is not carrier induced, as confirmed by electric-field effect measurements. Three-dimensional atom probe tomography shows that Co ions are randomly distributed, indicating that Co clustering or spinodal decomposition is not the origin of the ferromagnetism either. One possible mechanism for the ferromagnetism is hydrogen-facilitated interaction, which is supported experimentally by magnetic measurements on hydrogen-treated ZnO:Co as well as theoretically by first-principles calculation.
ISSN:1098-0121
1550-235X
DOI:10.1103/PhysRevB.85.174430