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 (111), barium (11) 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 degrees 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 degrees 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 angstrom and e = 23.199 angstrom. The samples exhibited a Curie point (T-c) of 452 degrees C and displayed ferromagnetic resonance characteristics centred on a frequency of 500 MHz. (C) 2006 Elsevier B.V. All rights reserved.