| Summary: | The paper is concerned with structural, morphological and magnetic properties of magnetite–silica magnetic fluids. The granulometric composition of the magnetic fluids was investigated by scanning and transmission electron microscopy, the phase composition was studied by X-ray diffraction and reflection high-energy electron diffraction, and magnetic properties were studied by vibrating sample magnetometry. In order to reveal the particle size distribution, dynamic light scattering and a proposed modification of depolarized dynamic light scattering were employed. The shape and dimensions of magnetic nanoparticles and also their aggregates are described. While the aspect ratio for the aggregates was 0.5–0.99, individual nanoparticles had an average aspect ratio of 0.9 and were nearly spherical. The sedimentation stability of a diluted magnetic fluid was also investigated. When the fluids were diluted 200 times, the stability was partially lost, and the nanoparticles aggregated, thereby forming clusters, and precipitated.
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