The Effect of Co and Zr Substitution on Morphological and Magnetic properties of Sr-hexaferrite by sol-gel method

Nano-size M-type hexaferrites SrFe_12-2x-y(CoZr)_xO₁₉ (x = 0.2, 0.6, 0.8, 1.0) powders are synthesized by using the sol-gel combustion method in nitrate citric acid systems. The X-ray diffraction pattern at room temperature shows that the prepared samples have a single phase and the effect of composition on the unit cell parameters, density and porosity has been studied. The X-ray diffraction patterns of SrFe_12-2x-y(CoZr)_xO₁₉ annealed at 750 manifest that all the species have hexagonal crystal structure with lattice constantsof a = 5.80–5.86 Å and c = 22.08–22.21 Å. TEM observation of as-burnt powders of SrFe_12-2x-y(CoZr)_xO₁₉ shows the powder particles have an average particle size of 14–29 nm. The magnetic properties have been investigated as a function of substitution of Co and Zr ions at applied field 15 kOe. The magnetic properties have been characterized by taking into account microstructure and preferential site occupancy of sublattice sites by substituted ions. Curie temperature increases with substitution due to strong of superexchange interaction. The change in magnetic parameters results in possible use of substituted ferrite for recording media.