Structural, dielectric and magnetic properties of nano-sized CoFe₂O₄ employing various synthesis techniques for high frequency and magneto recording devices: a comparative analysis

CoFe₂O₄ consisting of nanocrystallites were synthesized using glycine nitrate auto combustion, co-precipitation method and solid-state techniques. Both glycine nitrate auto combustion and co-precipitation method yielded nanosized CoFe₂O₄ (∼30–50 nm) particles whereas solid-state technique produced micron-sized (∼150 nm) cobalt ferrite particles. XRD and FTIR analysis confirmed the formation of the spinel CoFe₂O₄ structure. The frequency dependence of the dielectric constant for all the samples in the range 100 Hz–1 MHz, investigated in temperature regime of room temperature to 300 °C exhibited Maxwell-Wagner type interfacial polarization in consonance with Koop's phenomenological theory. Magnetic measurements were found to be strongly reliant on the particle size. Saturation magnetization decreased with decrease in particle size whereas the coercivity was found to increase from 1954 Oe to 2645 Oe as the particle size was reduced from 180 nm to about 24 nm. These deviations in the magnetic properties are ascribed to the grain size effects and cation redistribution, hence different synthesis techniques can lead to varied particle sizes and magnetic properties. Moreover, CoFe₂O₄ sample synthesized using sol-gel auto combustion technique find suitability in high frequency and magneto recording devices. (paper)