I. K. Gopalakrishnan

The structural and magnetization studies of Co-doped ZnO co-doped with Cu: Synthesized by co-precipitation method

Co- and Cu-doped ZnO of nominal composition Zn0.95Co0.05O and Zn0.94Co0.05Cu0.01O were synthesized by a co-precipitation method in organic media. Rietveld refinement of X-ray diffraction data of the samples annealed at 725 K showed that they are single phase without any secondary phases. DC magnetization measurements of samples with Cu co-doping (Zn0.94Co0.05Cu0.01O) as a function of field at room temperature showed a ferromagnetic signature while the samples without Cu co-doping (Zn0.95Co0.05O) are paramagnetic in nature. Both the samples heated at 1075 K are found to be paramagnetic at room temperature. Resistivity measurements above room temperature clearly showed a semiconducting behavior with a decreased resistivity value for Zn0.94Co0.05Cu0.01O compared to Zn0.95Co0.05O and ZnO, confirming additional carriers in Zn0.94Co0.05Cu0.01O due to Cu co-doping. Our results are in agreement with a recent computational study that doping additional carriers are necessary for realizing room temperature ferromagnetism in Co-doped ZnO.

Structural and magnetic properties of (In1−xFex)2O3 (0.0⩽x⩽0.25) system: Prepared by gel combustion method

(In1-xFex)2O3 polycrystalline samples with x = (0.0, 0.05, 0.10, 0.15, 0.20 and 0.25) have been synthesized by a gel combustion method. Reitveld refinement analysis of X raydiffraction data indicated the formation of single phase cubic bixbyite structure without any parasitic phases. This observation is further confirmed by high resolution transmission electron microscopy (HRTEM) imaging, and indexing of the selected-area electron diffraction (SAED) patterns, X-ray Absorption Spectroscopy (XAS) and Raman Spectroscopy. DC Magnetization studies as a function of temperature and field indicatethat they are ferromagnetic with Curie temperature (TC) well above room temperature.

Magnetic properties of hydrogenated Li and Co doped ZnO nanoparticles

The effect of hydrogenation on the magnetic properties of Zn0.85Co0.05Li0.10O nanoparticles is presented. It was found that the sample hydrided at room temperature (RT) showed weak ferromagnetism, while that hydrided at 400°C showed robust ferromagnetism at room temperature. In both cases reheating the sample at 400°C in air converts it back into the paramagnetic state completely. The characterization of samples by x-ray and electron diffraction showed that room temperature ferromagnetism observed in the samples hydrogenated at RT is intrinsic in nature, whereas that observed in the samples hydrogenated at 400°C is partly due to the cobalt metal clusters.