Abstract
Spinel ferrite having composition Ni
0.4
Co
0.4
Mg
0.2
Fe
2
O
4
was prepared by sol-gel method. X-ray diffraction result indicates that the ferrite sample has a cubic spinel type structure. FT-IR showed two absorption bands (ν
1
and ν
2
) that are attributed to the stretching vibration of tetrahedral and octahedral sites. Complex impedance properties have been investigated in 200-420 K temperature range with varying frequency between 40 and 10
7
Hz. Frequency and temperature dependency of imaginary part of permittivity (ϵ″) and dielectric loss (tanδ) has been discussed in terms of hopping of charge carriers between Fe
2+
and Fe
3+
ions. Activation energy has been estimated from both temperature dependency of dc conductivity and relaxation time data, which indicates that the relaxation process and conductivity have the same origin. Nyquist plots of impedance show semicircle arcs for sample and an electrical equivalent circuit has been proposed to explain the impedance results.