부산대학교 도서관

Distribution of chemical elements in polycrystalline BaFe12–xTixO19 and BaFe12–xMnxO19 barium ferrite samples is studied. The samples are prepared by solid-phase synthesis at 1400 °C from stoichiometric mixtures of oxides and carbonates. The XRD data indicate that all the studied samples have one crystalline phase characteristic of the M-type hexaferrite structure. The Curie temperatures are determined by differential scanning calorimetry. It is shown that replacing iron with Ti and Mn atoms diminishes the temperature of magnetic phase transition. The difference in bulk and surface atomic composition between the studied ferrites are established by XRD and XPS. It is shown that barium can exhibit surface segregation. The replacement of iron by manganese in the barium hexaferrite structure leads to surface segregation of barium, while the replacement by titanium hinders the segregation. [ABSTRACT FROM AUTHOR]