Connectivity between electrical conduction and thermally activated grain size evolution in Ho-doped CoFe2O4 ferrite

Ho-doped CoFe2O4 spinel ferrite has been synthesized by a combination of mechanical alloying and subsequent annealing of the alloyed powder in the temperature range 950 0C ≤ TAN ≤ 1200 0C. The grains of the nanocrystalline samples have been found in the single domain/pseudo-single domain state for TAN ≤ 1050 0C and multi-domain state for TAN ≥ 1100 0C. The room temperature Fourier transform infrared spectroscopy spectrum of the samples indicated substantial changes in the tetrahedral sites of the cubic spinel structure while the alloyed powder was annealed at different temperatures. Ac conductivity of the nano-grained samples has been studied in the frequency range 1 Hz-3 MHz and temperature range 303-523 K. This work has been specifically designed to highlight the properties of electrical conductivity in the annealed samples. Experimental results revealed a strong connectivity between electrical conduction and the single domain and multi-domain states of the grains.