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Highlights • Sm3+ incorporation maintained single phase cubic structure of Ni-Co ferrite. • Lattice strain with Sm3+ was increased. • FESEM micrographs exhibited agglomeration of grains with size varying from 40–60 nm. • Saturation magnetization upto x = 0.1 was decreased while for x = 0.125 it increases. • Observed Canting effect reveal the non-collinear structure. Abstract Samarium doped nanoferrites Ni 0.5 Co 0.5 Sm x Fe 2−x O 4 with (x = 0.00, 0.025, 0.05, 0.075, 0.10, 0.125) samples were prepared by using auto-combustion route. XRD pattern analysis confirmed the single-phase cubic spinel structure with no evidence of secondary phase. It is observed that, the lattice constant decreased from 8.342 Å (x = 0) to 8.321 Å (0.100) and again increased to 8.370 for x = 0.125. The crystallite size and particle size indicate the nano sized nature of the prepared ferrites. Crystalite size varies nonlinearly between 33 nm and 25 nm with addition of Sm3+ content in Ni-Co nanoferrites. The agglomerated grain structure revealed the high surface interaction among magnetic nanoparticles. FTIR spectra revealed the characteristics features of ferrite skeleton formation. The saturation magnetization, coercivity and remanence magnetization are found to decreases with the substitution of Sm3+ ions. [ABSTRACT FROM AUTHOR]

Rare earth Neodymium (Nd 3+ ) doped nanocrystalline Ni-Co mixed spinel ferrites which are chemically represented as Ni 0.5 Co 0.5 Nd x Fe 2-x O 4 (x = 0.025 to 0.125, in the step of 0.025) were synthesized by sol-gel auto-combustion method. The structural, morphological, infrared and magnetic properties were studied in detail in the light of Nd 3+ doping using standard techniques. X-ray analysis reveals the formation of single phase cubic spinel structure for all the prepared samples without any impurity phase. The crystallite size calculated from Scherrer's formula was observed to be decreasing with increasing Nd 3+ content. The lattice parameter calculated using XRD data was found to be decreasing upto x = 0.100 and then increases for x = 0.125. X-ray density was observed to be increasing from 5.327 to 5.630 gm/cm 3 . Surface morphology was studied through scanning electron microscopy technique. Grain size calculated from SEM analysis was found to be in the range of 30–59 nm. From transmission electron microscopy study, the average particle size was observed to be in the range of 35–45 nm. FTIR results exhibit the characteristics cubic spinel ferrite nature of the samples with two prominent absorption bands near 400 cm −1 and 600 cm −1 . FTIR also confirms the incorporation of Nd 3+ in the crystal structure. The magnetic behavior shows strong influence of substitution of Nd 3+ ions. The saturation magnetization, coercivity and remenance magnetization all decrease with substitution of Nd 3+ ions up to x = 0.100. For further increase in Nd 3+ concentration (x = 0.125), the saturation magnetization found to be increased. [ABSTRACT FROM AUTHOR]