Magnetite (Fe 3 O 4 ) nanoparticles (NPs) and SiO 2 -coated Fe 3 O 4 nanoparticles have successfully been synthesized using co-precipitation and modified Stöber methods, respectively. The samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), vibrating sample magnetometer (VSM) techniques, X-ray absorption spectroscopy (XAS), and X-ray magnetic circular dichroism (XMCD). XRD and FTIR data confirmed the structural configuration of a single-phase Fe 3 O 4 and the successful formation of SiO 2 -coated Fe 3 O 4 NPs. XRD also confirmed that we have succeeded to synthesize nano-meter size of Fe 3 O 4 NPs. HRTEM images showed the increasing thickness of SiO 2 -coated Fe 3 O 4 with the addition of the Tetraethyl Orthosilicate (TEOS). Room temperature VSM analysis showed the magnetic behaviour of Fe 3 O 4 and its variations that occurred after SiO 2 coating. The magnetic behaviour is further authenticated by XAS spectra analysis which cleared about the existence of SiO 2 shells that have transformed the crystal as well as the local structures of the magnetite NPs. We have performed XMCD measurements, which is a powerful element-specific technique to find out the origin of magnetization in SiO 2 -coated Fe 3 O 4 NPs, that verified a decrease in magnetization with increasing thickness of the SiO 2 coating. Graphical Abstract Magnetite (Fe 3 O 4 ) nanoparticles (NPs) and SiO 2 -coated Fe 3 O 4 nanoparticles have successfully been synthesized using co-precipitation and modified Stöber methods, respectively. The samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), vibrating sample magnetometer (VSM) techniques, X-ray absorption spectroscopy (XAS), and X-ray magnetic circular dichroism (XMCD). XRD and FTIR data confirmed the structural configuration of a single-phase Fe 3 O 4 and the successful formation of SiO 2 -coated Fe 3 O 4 NPs. XRD also confirmed that we have succeeded to sy...

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