Structural and magneto-elastic properties of samarium doped cobalt–nickel ferrite ceramics obtained by spark plasma sintering

The present work focused on fabricating and characterizing the magneto-structural properties of pure spinel ferrite nanoparticles and Co0.8Ni0.2Fe2-xSmxO4 (x = 0.01, 0.02) using the sol-gel method, and then producing pellets using the spark plasma sintering technique. The composition, structure, and microstructure of the nanoparticles and pellets were characterized by different techniques such as X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The average nanoparticle sizes were between 18 and 25 nm. Rietveld refinement was performed using the FullProf Suite program to confirm the cubic phase (Fd-3m, space group 227) to calculate lattice parameters, crystallite size, and microstrain values using the pseudo-Voigt and Thompson-Cox-Hastings functions. Adding Ni2+ and Sm3+ ions led to a reduction in the lattice parameter and crystallite size of 8.355 Å and 7.14 nm, respectively. Magnetization curves and magnetic hysteresis loops were measured to determine and evaluate the coercive field, remanent magnetization, and saturation up to a maximum magnetic field of 20 kOe at room temperature. A decrease in the magnetic properties of replacing Co2+ with Ni2+ and Fe3+ with Sm3+ was attributed to the reduction in magnetocrystalline anisotropy. Finally, a dilatometry measurement to calculate their magnetostrictive coefficient, obtaining the highest value for pure cobalt ferrite at -169 ppm, followed by a decrease to -100 ppm and -109 ppm when Ni2+ and Sm3+ were added, respectively. However, the magnetic field required to reach saturation was lower in dopped samples than pure ferrite, with an increase in magnetostrictive saturation at a lower applied field.