Coercivity enhancement of strontium hexaferrite nano-crystallites through morphology controlled annealing

摘要: Abstract In order to improve the performance of ferrite based permanent magnet materials, evolution magnetic properties with increasing particle size anisotropic SrFe12O19 nano-platelets is investigated, allowing elucidation stable single domain (SSD) size. Phase-pure, ultra-thin platelet-shaped strontium hexaferrite (SrFe12O19) nano-crystallites have been successfully synthesized using a simple, green and scalable supercritical hydrothermal flow method. The reactor precursor prepared from aqueous solutions nitrate, iron nitrate sodium hydroxide. samples were subsequently annealed at different temperatures (600–1100 °C) in intervals between 1 68 h tune morphology. grow anisotropically, pronounced growth along c-axis, which coincides easy axis. annealing treatment gives rise variations platelet aspect ratio. Microstructural investigations by transmission electron microscopy (TEM) Rietveld refinement powder X-ray diffraction (PXRD) data, combined vibrating sample magnetometry (VSM), reveal significant correlation morphology, on macroscopic produced powders. optimal single-domain crystallite dimensions are found PXRD be 62 nm thick 76 nm wide, attaining coercivity (Hc) 459(10) kA/m (5.77 kOe), saturation magnetization (Ms) 74.0(1) Am2/kg. A theoretical critical for particles proposed, disc-shaped ellipsoidal model combination obtained experimental results. Particle shape revealed an enormous influence SSD size, varying significantly compared isotropic particles, thus underlying need meticulous characterization optimize specific systems.