Structural and Magnetic Properties Evolution of Co-Nd Substituted M-type Hexagonal Strontium Ferrites Synthesized by Ball-Milling-Assisted Ceramic Process

M-type hexagonal Sr 1− x Co x Nd x Fe 12− x O 19 ( x = 0, 0.08, 0.16, and 0.24) has been synthesized by ball milling, followed by calcination in air. The calcined products have been characterized by x-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra, and vibrating sample magnetometry. XRD and SEM analyses confirm the formation of M-type Sr hexaferrite with platelet-like morphology when Sr 1− x Co x Nd x Fe 12− x O 19 ( x = 0, 0.08, 0.16, and 0.24) precursors are calcined at 950°C in air for 2.5 h. Lattice parameters “ a ” and “ c ” values of Sr 1− x Co x Nd x Fe 12− x O 19 reflect a very small variation after doping of Nd 3+ and Co 2+ ions. Average crystallite size of Sr 1− x Co x Nd x Fe 12− x O 19 sample, calcined at 1150°C, decreased obviously after doping of Co 2+ and Nd 3+ ions. This is because the bond energy of Nd 3+ -O 2− is much larger than that of Sr 2+ -O 2− . Magnetic characterization indicates that all the samples exhibit good magnetic properties. Substitution of Sr 2+ and Fe 3+ ions by Nd 3+ and Co 2+ ions can improve the specific saturation magnetizations and remanence of Sr 1− x Co x Nd x Fe 12− x O 19 . Sr 0.84 Co 0.16 Nd 0.16 Fe 11.84 O 19 , calcined at 1050°C, has the highest specific saturation magnetization value (74.75 ± 0.60 emu/g), remanence (45.15 ± 0.32 emu/g), and magnetic moment (14.34 ± 0.11 μ B ); SrFe 12 O 19 , calcined at 1150°C, has the highest coercivity value (4037.01 ± 42.39 Oe). These magnetic parameters make this material a promising candidate for applications such as high-density magnetic recording and microwave absorbing materials.