Tuning ferromagnetism in zinc oxide nanoparticles by replacing Zn2+ ions ions with Cr3+ ions ions

This paper presents the influence of replacing divalent Zn(2+ )ions of the ZnO by trivalent Cr3+ ions on their structural, optical and magnetic properties. Samples of Zn1-xCrxO (where x = 0.001-0.004) are synthesized using the microwave irradiated solvothermal method. The X-ray diffraction pattern confirms the single-phase wurtzite hexagonal structure of ZnO nanoparticles and the average size of the samples is found to be 10.3-19nm. The morphology and chemical composition of the samples are found out using Scanning electron microscopy with energy dispersive X-ray analysis. Transmission electron microscopy results show the formation of quasi-hexagonal nanoparticles whereas Fourier transform infrared spectroscopy studies identify the presence of a functional group in the samples. The ultra-violet-visible spectrum shows a blue shift in the absorption edge. The presence of oxygen related defects in the samples is confirmed by photoluminescence spectroscopy studies. Defect related bands are identified from the value of Lande splitting factor "g" with the help of electron spin resonance spectroscopy studies. Vibrating sample magnetometer studies exhibit room temperature ferromagnetic properties for all samples. Due to the existence of oxygen-related defects, the saturation magnetization increases with increasing in Cr concentrations.