Increase in initial permeability due to substitution of high spin cations in nanocrystalline Ni–Mg ferrites

In order to increase the permeability, high spin Mn2+ substituted nanocrystalline Ni0.50−xMnxMg0.5Fe2O4 were synthesized by the combustion technique. Mn2+ substitution acts as an accelerator of grain growth and uniform grain distribution in these chemical compositions. Both the real part of initial permeability and the saturation magnetization increase with increasing Mn content up to x=0.30 and they decrease for higher Mn2+ content indicating the possibility of a non-collinear spin arrangement between tetrahedral and octahedral sites. The maximum increase of initial permeability is 54% compared to that of parent composition. The weakening of exchange interaction may be confirmed by increasing lattice parameter and decreasing Néel temperature with increasing Mn2+ content.

► Phase pure nanocrystalline mixed ferrites are prepared by the combustion technique.
► There is an enhancement of microstructures due to Mn2+ substitution.
► Initial permeability enhances about 54% for the sample sintered at 1623 K.
► Room temperature Ms increases up to x  =0.30 and then decreases.
► Increase in μi/ and Ms due to high spin Mn2+ substitution is explained thoroughly.