Europhys. Lett.
Volume 72, Number 1, October 2005
Page(s) 76 - 82
Section Condensed matter: structural, mechanical and thermal properties
Published online 26 August 2005
Europhys. Lett., 72 (1), pp. 76-82 (2005)
DOI: 10.1209/epl/i2005-10191-2

The formation of precipitates in the $\chem{ZnCoO}$ system

H.-J. Lee1, S. H. Choi2, C. R. Cho3, H. K. Kim1 and S.-Y. Jeong1, 4

1  Research Center for Dielectric and Advanced Matter Physics (RCDAMP) Pusan National University - Busan 609-735, Korea
2  Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH) - Pohang 790-784, Korea
3  Busan Center, Korea Basic Science Institute (KBSI) - Busan 609-735, Korea
4  School of Nano-Science and Technology, Pusan National University Busan 609-735, Korea

received 11 March 2005; accepted in final form 26 July 2005
published online 26 August 2005

Magnetic matter such as transition metals or metal oxides are able to exhibit ferromagnetism by the clustering in magnetic semiconductors. We fabricated Co-doped ZnO samples using the sol-gel method, and studied the magnetic precipitates in the samples by using both neutron diffraction and X-ray absorption fine-structure measurements. The structural details were characterized by X-ray and neutron diffraction, and the data were interpreted using Rietveld refinement. The doped Co ion was fully substituted into a ZnO lattice at 5 $\un{mol\%}$, but the secondary phase of the Co3O4 was formed above 5 $\un{mol\%}$ of Co doping and its neutron diffraction signal increased up to 20 $\un{mol\%}$. The quantitative amounts of each phase were calculated to be 55.43 $\un{wt.\%}$ of Co3O4 and 44.57 $\un{wt.\%}$ of fully cobalt-substituted ZnO. In the 30 $\un{mol\%}$ Co-doped sample, Co metal, as well as oxidized Co, were identified in this study. Those signals, however, were not observed by X-ray diffraction. To verify the local chemical bonding state, we used extended X-ray absorption fine-structure measurement and investigated the formation of precipitates by calculating the inter-atomic distance using Fourier analysis.

61.12.Ld - Neutron diffraction.
61.10.Ht - X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
75.50.Pp - Magnetic semiconductors.

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