Magnetic and structural properties of M-type barium hexaferrite prepared by co-precipitation

Stoichiometric and single-phase barium hexaferrite (BaM) has been synthesized by co-precipitation and an additional solid state preparative method using high-purity nitrates, oxides and carbonates of iron (III), barium (II) and ammonium hydroxide. The isochronally and isothermally measured permeability and magnetic loss tangents over 1 MHz–1 GHz in frequency remained moderately constant until a sintering temperature of 1300 °C where relative permeability of 1.3 and loss tangent of 0.06 at 1 GHz, indicate high-frequency magnetic characteristics for BaM. TGA/DTA studies showed the hexaferrite formation temperature was found to be 1050 °C. The apparent densities before and after each firing cycle showed a monotonic increase. X-ray diffraction studies established the presence of a single phase with the theoretical space group P63/mmc, and computed cell parameters of a=b=5.895 Å and c=23.199 Å. The samples exhibited a Curie point (Tc) of 452 °C and displayed ferromagnetic resonance characteristics centred on a frequency of 500 MHz.