The investigation of microstructure, optical and electromagnetic properties of powder prepared from Nd-compound doped Al6Si9Fe85 (Alsifer) alloy. The result of energy-dispersive X-ray spectroscopy is an evidence that the complementary Nd-containing Nd-Fe phase is on the surface of Alsifer particles. The magnetic particles distribution histogram in powder after mechanical treatment was plotted and analyzed. The electromagnetic properties (components magnetic permeability and dielectric permittivity) for produced composites with Nd-compound doped Alsifer powder with 50-90% (wt.) was studied. The nonlinear concentration dependence of magnetic and dielectric permittivity versus concentration Nd-compound doped Alsifer particles was observed. The magnetic resonance in composites was detected that shifted in low frequencies with increased magnetic filler concentration. The resonance field, absorption linewidth, g-factor and microwave absorption ability of Nd-compound doped Alsifer powder were determined from FMR experiment.

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The magnesium nanosized ferrite powder with formula MgFe2O4 was synthesized via a pyrochemical sol–gel glycine–nitrate method and annealed consistently at temperatures of up to 1300 °C. The MgFe2O4 ferrite samples’ microstructure was studied by SEM and XRD methods. According to the results of the studies, the increase in MgFe2O4 nanoparticles size from about 15 nm to micron-sized particles was observed when increasing annealing temperatures. The DC electrical conductivity of MgFe2O4 also clearly shows the change in conduction behavior of samples with increased calcination temperatures. The electromagnetic microwave properties of micron-sized particles of MgFe2O4 ferrite powder for a 1200 °C annealing temperature were studied for composites in paraffin matrix with produced magnetic filler mass concentration at 40% and 50%. The filament composites of polymer polylactic acid with MgFe2O4 ferrite powder samples were prepared by the FDM 3D-printing process and their microwave-absorbing properties were investigated. The application of developed PLA–MgFe2O4 ferrite filament for fabricating magnetic microwave-absorbing components also was demonstrated.

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