Local investigation of hyperfine interactions in pure and Co-doped ZnO

Abstract

In the present work bulk samples of pure as well as Co-doped ZnO with different concentrations were prepared by sol–gel method from highly pure metallic Zn (99.9999%) and Co (99.9999%). The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray microanalysis (EDS) and perturbed gamma–gamma angular correlation (PAC) spectroscopy. Carrier-free 111In nuclei were introduced during preparation of the samples and used as probe nuclei at Zn sites for PAC measurements. PAC results show that both pure and Zn1 xCoxO(xr0:15) samples have the same electric quadrupole frequency when Co-doped samples are annealed in air, argon or nitrogen atmosphere at 1173K. SEM and EDS results showed that Co-doped samples are homogeneous without any secondary Co phases. These observations indicate that Co ions are substituted for Zn ions and have a similar electronic structure of Zn ions. A weak local magnetism was observed at temperatures below about 300K for Co concentration of 10% when sample was annealed in Nitrogen.