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

Non-stoichiometric Nd–Co substituted hexaferrites of composition Sr1−xNdxFe12(1−x)CoxO19 (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 MS increased from 72 to 76 Am2/kg (x=0–0.2), while coercivity Hc increased from 26.40 to 58.70 A/m (x=0–0.3). Nd–Co substitutions enhance magnetic properties in deficient iron Sr hexaferrites.