Effect of Zn substitution on structural, dielectric and magnetic properties of nanocrystalline Co_1−xZn_xFe₂O₄ for potential high density recording media

Co_1−xZn_xFe₂O₄ (0 ≤ x ≥ 1) nanopowders were synthesized using microwave hydrothermal method. The synthesized powders were characterized by X-ray diffraction and transmission electron microscope (TEM). The average particle size was obtained from TEM and it is found to be 17 nm. Then powders were sintered using microwave sintering method at 900 °C/15 min. The real part of permittivity varies as Zn concentration increases and the resonance frequency was observed at much higher frequencies (>1 GHz) and there is a significant decrease in the loss factor. The dielectric parameters were observed to decrease with the increased Zn contents. The frequency dependent dielectric properties of all these nanomaterials have been explained qualitatively in accordance with Koop’s phenomenological theory. The magnetic permeability spectra exhibit resonance and anti-resonance type behaviour. Lower reduced remnant magnetization (M_r/M_s) values (x < 0.5) suggest that all the samples have uniaxial anisotropy. The increasing trend of magnetic parameters (coercivity and retentivity) is consistent with crystallinity. The moderate magnetization and high coercivity are enough to attain considerable signal to noise ratio in high density recording media.