Abstract
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•All products present superparamagnetic behavior at room temperature (RT).•The high Ms and magnetic moment values are attributed to cation distribution change.•The greater magnitude of band gap for the coated samples proves the existence of magnetic and nonmagnetic shells.
In this study, thermal decomposition approach was used for the synthesis of super-paramagnetic triethylene glycol (TEG)-stabilized Mn1−xZnxFe2O4 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) nanoparticles. The change in the magneto-optical properties of the products due to TEG stabilization were investigated. The composition, phase, magnetic and optical properties were determined by X-ray diffraction, transmission/scanning electron microscopy and vibrating sample magnetometer, UV–Vis spectrophotometer respectively. The triethylene glycol was used as both coordination and stabilizing agent. X-ray powder diffraction and Transmission electron analysis showed that all samples have narrow size distribution in the range of 8–6nm. Room temperature VSM magnetization measurements on 3 selected NPs exhibit superparamagnetic behavior. This characteristic behavior can be generalized for all TEG-stabilized Mn1–xZnxFe2O4 NPs. Saturation magnetization (Ms) of TEG-stabilized ZnFe2O4 NPs is 32.90emu/g is much greater than the bulk Ms value of 5emu/g. This case is attributed to cation distribution change from normal spinel to mixed structure. The average crystallite size (Dmag) was estimated from the Langevin fit studies performed on M–H hysteresis loops. The obtained average Dmag values are about 6nm and this diameter is in great accordance with the results calculated from XRD measurements. Diffuse reflectance spectroscopy was applied to determine the optical properties of samples. The optical direct band gap values of TEG-stabilized Mn1−xZnxFe2O4 NPs are minimum (2.05eV) for MnFe2O4 NPs and maximum (2.86eV) for ZnFe2O4 NPs. These calculated values are much higher than the band gap values given in the literature for uncoated Mn1−xZnxFe2O4 NPs.