The influence of Nd-Co substitution on the magnetic properties of non-stoichiometric strontium hexaferrite nanoparticles

Non-stoichiometric Nd-Co substituted hexaferrites of composition Sr_1−xNd_xFe_12(1−x)Co_xO₁₉ (x=0-0.4) were prepared by the self-propagating combustion method and subsequent heat treatments. Structural characterization of samples showed that the M-type hexagonal structure can be maintained for substitutions x<0.4 without the segregation of secondary phases on samples calcined at 1100 °C. The crystallites sizes range between 50 and 70 nm. Mössbauer spectroscopy results indicate that the iron vacancies are not evenly distributed over the lattice and that Co/Fe substitution mainly takes place in site 4f2. Magnetic measurements reveal that values of saturation magnetization M_S increased from 72 to 76 Am²/kg (x=0-0.2), while coercivity H_c increased from 26.40 to 58.70 A/m (x=0-0.3). Nd-Co substitutions enhance magnetic properties in deficient iron Sr hexaferrites.