An Atomic-Scale Justification for the Weak Ferromagnetism Observed in Nanostructured Zn_0.96–xCo_xMn_0.04O Powders

Abstract

For this study, cobalt-doped Zn 0.96 Mn 0.04 O (Zn 0.96−x Co x Mn 0.04 O) nanoparticles were prepared using a sol−gel route by varying the Co doping (with x = 0.02, 0.04, and 0.06). The prepared samples were characterized in terms of their structural and magnetic properties. X-ray diffraction (XRD) revealed a nanocrystalline nature with a hexagonal wurtzite structure with P6 3 mc crystal symmetry. The Rietveld refinement method was employed to determine the lattice constant, and it was found that the lattice volume decreased slightly with Co doping due to the replacement of Zn by Co with nearly the same ionic radius. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were performed to analyze the morphology and elemental analysis of the studied samples. Room-temperature magnetic measurements indicated weak ferromagnetic behavior in all samples. Density functional theory (DFT) calculations show that Mn atoms prefer an in-plane configuration, while Co adopts an out-of-plane arrangement. Mn atoms acquire an antiferromagnetic configuration, while Co is ferromagnetic and sits near Mn atoms. Therefore, the weak ferromagnetism at room temperature could be attributed to larger FM zones induced by the proximity of Mn and Co. The density of states shows that, for all cases, the codoped ZnO remains a semiconductor material, proving its usefulness as a diluted magnetic semiconductor for spintronics devices operating at room temperature.