Tailored magnetic properties of Sm(Zn) substituted nanocrystalline barium hexaferrites

Sm and SmZn substituted nanocrystalline barium hexaferrites (Ba1-xSmxFe12O19 and Ba1-xSmxFe12-xZnxO19, x = 0-0.6) were prepared by the sol-gel autocombustion process. X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) were used to characterize the phase composition, crystal structure and magnetic properties of the as-prepared barium hexaferrites. All results indicated that the substitution content (x) critically influenced on the phase composition and magnetic properties. When the substitution content x > 0.2, impurity phases such as alpha-Fe2O3, SmFeO3 and ZnFe2O4 were detected, which diluted and weakened saturation magnetization (M-s). For the Sm-doped samples, owing to the hyperfine field, canting spin, magnetic dilution and impurity phases, M-s increased with x firstly, and then decreased when x > 0.03. On the other hand, the coercivity (Hc) continuously increased with x. Nevertheless, for the SmZn-doped samples, M-s reached maximum when x = 0.06 and Hc almost unchanged with x. Compared the magnetic properties of Sm- and SmZn-doped samples, it was proved that Zn2+ substituted Fe3+ at 4f(2) sites and Sm3+ substituted Ba2+, which changed Fe3+ to Fe2+ at 2a sites in order to satisfy the electroneutrality principle. (C) 2009 Elsevier B.V. All rights reserved.