The annealing temperature dependence of magnetic properties in Sr-ferrite nanoparticles

The SrFe12O19 powders prepared by a sol-gel method were annealed at temperatures ranging from 400 degreesC to 900 degreesC for 3 h and 6 h in air. Magnetic and structural properties of the powders were characterized with a vibrating sample magnetometer (VSM), X-ray diffractometer (XRD), scanning electron spectroscopy (SEM), Mossbauer spectroscopy, thermogravimetry (TG), and differential thermal analysis (DTA). M-type hexagonal phase is observed in the samples annealed at temperatures above 600degreesC by XRD. In the sample annealed at 800degreesC, lattice constants are a(0) = 5.9227 Angstrom c(0) = 23.2368 Angstrom and particle size was about 74 nm. The coercivity of the samples increased from 6.2 Oe for the powder annealed at 500 1 C to 7000 Oe for annealed powder at 800 degreesC. The saturation magnetization increased from 30.7 emu/g to 63.0 emu/g as annealing temperature is increased from 500degreesC to 800degreesC.