Search for Room Temperature Ferromagnetism in Low-Concentration Transition Metal Doped ZnO Nanocrystalline Powders Using a Microscopic Technique

The local structural and electronic environment around $^{111}$Cd guest atoms in pure and transition metal doped Zn$_{1 - x}$ TM$_{\rm x}$ O nanocrystalline powders ($\hbox{TM}=\hbox{Co}$ , Mn, Cu and ${\rm x}= \hbox{0.01, 0.02, 0.05}$) was monitored on an atomic scale, by perturbed angular correlation (PAC) spectroscopy, with high precision. For these measurements, the single phase nanocrystalline powders were synthesized at low annealing temperature by sol-gel Pechini method. Samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and PAC spectroscopy. The XRD pattern of these powder samples confirmed the presence of single phase nano-sized particles. The only well-defined oscillations observed by PAC measurements were those corresponding to the electric quadrupole interaction which have been attributed to the substitutional incorporation of the probe atoms at the cation sites of ZnO lattice. The present measurements did not reveal any evidence of ferromagnetic behavior in pure or doped ZnO nanopowders.