We prepared the magnetic cenospheres deposited with magnetite Fe3O4nanoparticles under hydrothermal conditions. The crystalline phase, magnetization properties, morphology, chemical composition and thermal stability of asobtained cenospheres are analyzed by Xray diffraction, vibrating sample magnetometer, scanning electron microscope, Xray energy dispersive spectroscope, transmission electron microscope, thermal gravimetric analysis and differential scanning calorimetry techniques. The results show that the inverse cubic spinel phase of Fe3O4nanoparticles with an average size 50 nm are synthesized, and synchronously deposited on cenosphere surface. As the thickness of Fe3O4coating increases, the saturation magnetization increases to some extent. The growth of Fe3O4nanoparticles can be controlled by adding ethanol to the reaction solution.

Keywords: Structural and magnetic properties,sol-gel auto-combustion method, Ni 0.5 Zn 0.5 Sm x Fe 2-x O 4 nanoferrite Abstract. Samarium ion substituted magnesium of Ni 0.5 Zn 0.5 Sm x Fe 2-x O 4 spinel ferrite powders have been prepared by a sol-gel auto-combustion method. XRD results indicate that the production of a single cubic phase of ferrites. Some particles are agglomerated due to the presence of magnetic interactions among particles. The Mössbauer spectra of Ni 0.5 Zn 0.5 Sm x Fe 2-x O 4 nanocrystalline at room temperature show that the magnetic interaction and interface atomic state were influenced strongly by Sm 3+ ratio, and the saturation magnetization of a spinel ferrite largely also depends on Sm 3+ ratio and particle size, while the coercive field depends on Sm 3+ ratio, particle size and their shapes. The SEM micrographs indicate that the Nanocrystalline Particles' specific features and characteristics.