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

Li Li, Y. Guo, X. Y. Cui, Rongkun Zheng, K. Ohtani, C. Kong, A. V. Ceguerra, M. P. Moody, J. D. Ye, H. H. Tan, C. Jagadish, Hui Liu, C. Stampfl, H. Ohno, S. P. Ringer, F. Matsukura

Research output: Contribution to journalArticlepeer-review

51 Citations (Scopus)

Abstract

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 (0001̄) 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.

Original languageEnglish
Article number174430
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume85
Issue number17
DOIs
Publication statusPublished - 2012 May 23

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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