A comparative study of the structural and magnetic properties for Zn2+ and Ge4+ ions substituted nickel ferrites

[Display omitted] •The article presents a comparative structural and magnetic studies.•SEM reveals that the microstructure is greatly influenced by dopants addition.•Cation distribution is discussed based on magnetic moments from VSM.•Ni-Zn ferrites are promising candidates for recording media manufacturing. In this research, substitution of divalent (Zn2+) and tetravalent (Ge4+) ions into NiFe2O4 ceramic was explored to enhance the structural and magnetic properties. Two series of mixed nickel ferrites, Ni1-xZnxFe2O4 and Ni1+xGexFe2-2xO4, have been analogously inspected. XRD analysis evidenced that all compositions of the two systems were manufactured in a single-phase of nickel ferrite with cubic spinel structure. The lattice parameter increased significantly for Zn substitution from 0.833 to 0.837 nm, meanwhile decreased by adding Ge from 0.833 to 0.830 nm. The porosity rises from 5.24 to 6.81% with zinc substitution and from 5.24 to 10.27% with the inclusion of germanium due to the development of intra- and inter-granular pores. The grain diameter was increased considerably with Zn concentration from 1.29 to 6.47 µm, while changes slightly with germanium content from 1.29 to 2.24 µm. The magnetic measurements indicate that Ms increased significantly with increasing Zn2+ ions concentration, but decreased slightly with the addition of Ge4+ ions to nickel ferrite. In addition, the variation of the relative permeability (μr) with the applied magnetic field was discussed. Ni-Zn ferrite showed highest saturation magnetization, lowest coercivity and largest permeability, making it a suitable candidate for high frequency applications such as high density recording media compared to Ni–Ge ferrite. The initial permeability vs. temperature was measured from 300 K up to 900 K for all compositions. The Curie point was found to decrease with the addition of either Zn2+ or Ge4+ ions to nickel ferrite.