| Magnetic resonance could be very useful technique in clarification of many unresolved problems in nano-magnetism of ZnO doped with transition metal ions, in particular with Co. In the first part of this paper a review of investigations of ZnO:Co nanomaterials using magnetic resonance techniques - electron paramagnetic resonance (EPR) and ferromagnetic resonance (FMR) - is presented. The preparation methods, the structural characteristics of the obtained materials and the main results of EPR/FMR studies are briefly described. In the second part the EPR/FMR investigations of a new series of (CoO)n(ZnO)1-n nanocomposites (where the composition index n = 0.4, 0.5, 0.6 and 0.7) prepared by the hydrothermal synthesis have been presented. XRD measurements displayed peaks from ZnO and ZnCo2O4 phases as well as weak lines attributed to Co(OH)2 phase. The temperature and Co concentration dependence of the calculated EPR/FMR parameters (resonance fields, linewidths, integrated intensities) were studied. Three main components were recognized - a broad line attributed to nanoparticles of ZnCo2O4 phase, two narrow lines arising from Co2+ ions in ZnO nanoparticles, and a narrow component probably from the impurity Co3O4 phase. |
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