Conversion of Nano-Sized Spherical Magnetite to Spherical Barium Ferrite Nanoparticles for High Density Particulate Recording Media

Shape Dependent Coercivity Simulation of a Spherical Barium Ferrite (S-BaFe) Particle with Uniaxial Anisotropy

“…3(a) and 3(b) shows the hysteresis loops of a single 27 nm-S-BaFe particle by the three simulations. The experimental loop is also shown of a collection of nonoriented ~27 nm S-BaFe particles heat-treated at 750 °C for 5 h, which was previously reported [19].…”

“…On the other hand, the S-BaFe particle could possibly be a hexagonal prism, but surrounded by Fe x O y to give its spherical shape. This shape may be supported by Mössbauer spectra of S-BaFe nanoparticles with enhanced magnetic properties (coercivity of 4075 Oe, saturation magnetization of 41.4 emu/g, and remanent magnetic moment of 24.3 emu/g) formed by heat-treatment at 900°C for 2 h that showed the presence of residual hematite (α-Fe 2 O 3 ) phase [2].…”

“…The experimentally measured coercivity, saturation magnetization, and remanent magnetic moment of ~27 nm SBaFe particles are 3211 Oe, 38.7 emu/g, and 22.7 emu/g, respectively [19]. The saturation magnetization, M s , in emu/cm 3 was estimated using the well-known BaFe theoretical density of 5.29 g/cm 3 .…”

“…Spherical barium ferrite (S-BaFe: BaFe 12 O 19 ) particles have advantages over metal particles (MP) owing to a point-to-point contact for achieving high areal density for particulate recording media [1][2][3][4][5]. This is mainly because the MP requires a passivation layer that limits reduction of particle size due to low saturation magnetization and coercivity.…”

“…1(a), rather than being entirely spherical. The structure was surmised from TEM micrograh [2] with partial TEM micrograph shown in Fig. 1(b).…”