Abstract:

Nanopowders of Zn_{1−x−y−z}Mn_xNi_yLi_zO [(x = 0.04, y = 0, z = 0), (x = 0.04, y = 0.03, z = 0) and (x = 0.04, y = 0.03, z = 0.03)] have been synthesized by sol–gel precursor route using ethylene diamine tetraacetic acid (EDTA) as a metal chelating agent. X-ray diffraction analysis confirms the formation of wurtzite hexagonal structure for all the three compositions. Mn²⁺ doped ZnO exhibits room temperature ferromagnetism (RTFM), and it is found that further Ni²⁺ doping has decreased M_s because of limit of solid solubility of transition metal in ZnO. But codoping of monovalent Li¹⁺, further increases the ferromagnetism (FM) value, due to introduction of free carriers compared to the dual doped samples. Photoluminescence (PL) spectra of the system, exhibit near band edge (NBE) emission peak at ∼464 nm due to the electron transition from interstitials to the valence band. Recombination of conduction electron with hole trapped at oxygen vacancy, leads to prominent defect emission peaks at ∼482 nm and 532 nm. The evidence of the formation of metal–EDTA complexes are found from the Fourier transform infrared spectra at 2800–3800 cm⁻¹ with shifting, splitting of the peak and also drastic variations in the intensity.

Key words: Mn-doped, Dual doped, Li codoped, Ferromagnetism, Photoluminescence, Fourier transform infrared (FTIR) spectroscopy