Electric conduction in Ni–Zn ferrites

Abstract

The AC electrical conductivity was studied as function of temperature, frequency and composition for a series of Ni 1− x Zn x Fe 2O 4 ferrite samples prepared by usual ceramic technique. The experimental results indicated that the AC electrical conductivity σ 2( ω, T) increases while the activation energy for electric conduction in ferrimagnetic region E f decreases on increasing the frequency. The real AC ( σ AC′) and DC ( σ DC) electrical conductivities increase as the temperature increases indicating that the studied samples are semiconductors. Both σ AC′ and σ DC increase whereas the Curie temperature T c, activation energies for electric conduction E f and E p (in paramagnetic region) decrease as Zn ion substitution increases. The activation energy for electric conduction E p in the paramagnetic region is higher than that in ferrimagnetic region E f. The parameter B and exponent n for electrical conductivity σ 2( ω, T) in the power law σ 2( ω, T)= Bω n were found, respectively, to be composition and temperature dependent. Both n and B increase as Zn ion substitution increases. n decreases whereas B increases as the temperature increases. Empirical formulae were suggested for the temperature dependence of both n and B; compositional dependence of electrical conductivity σ, and compositional dependence of n and B.