Substitutional effect on structural and dielectric properties of Ni1−xAxFe2O4 (A = Mg, Zn) mixed spinel ferrites

The Ni1−xAxFe2O4 (A = Zn, Mg; x = 0.0, 0.5) ferrites synthesized by chemical co-precipitation method. X-ray diffraction and Raman spectroscopy reveals that all the ferrite samples are in single-phase cubic spinel structure with Fd3m space group. The lattice parameter enhances with Mg and Zn substitution. Raman spectroscopy identifies a doublet like nature of A1g mode for all the three ferrites. A blue shift in Mg doped ferrite and a red shift in Zn doped ferrite has been observed as compared to parent NiFe2O4. Frequency dependent dielectric response confirms the dielectric polarization and electrical conduction mechanism. The minimum value of loss tangent (∼0.03) at 5 KHz suggests that Ni1−xAxFe2O4 is effective material for microwave application. The activation energy for NiFe2O4, Ni0.5Mg0.5Fe2O4 and Ni0.5Zn0.5Fe2O4 are found to be 0.28 eV, 0.29 eV and 0.31 eV, respectively.