Influence of annealing temperature and doping rate on the magnetic properties of Zr–Mn substituted Sr-hexaferrite nanoparticles

A series of M-type strontium hexaferrite samples having nominal composition SrZrxMnxFe12−2xO19 (where x = 0.0–0.8) has been synthesized by the co-precipitation method. All the samples synthesized were of single magnetoplumbite phase. The particle size was found to be in the 40–65 nm range for the samples annealed at 1193 K while the samples annealed at 1443 K were in the 100–200 nm range. The saturation magnetization increase with temperature and reached maxima for the samples annealed at 1393 K and then start to decrease while the coercivity decreases regularly with temperature. The decrease in coercivity is due to the increase in the particle size of the sample with temperature. The saturation magnetization increase for the samples doped with Zr–Mn up to x = 0.4 doping rate and higher substitution lead to decrease in saturation magnetization. The coercivity decrease with the increase in Zr–Mn substitution. The behavior of saturation magnetization has been explained on the basis of occupation of the substituted cations at different iron sites. The increase in saturation magnetization and decrease in coercivity suggest that the synthesized materials can be used for the application of recording media.