Effect of site preferences on structural and magnetic switching properties of CO-Zr doped strontium hexaferrite SrCoxZrxFe(12-2x)O19

The aim of this work is to investigate the correlation between the distribution of cations over five crystallographic sublattices and magnetic properties of Sr-hexaferrites in the coupled substitution of magnetic Co2+ and non-magnetic Zr4+ for Fe3+. During present work, we have synthesized a series of SrCox ZrxFe(12-2x)O19 ferrites (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) using sol-gel route at a much lower temperature of 800 degrees C. These compounds were characterized by TGA, FT-IR, XRD, EDS and TEM. XRD data reveal the formation of polycrystalline magnetoplubite structure for all the compounds of the series. The crystallite size of nanoparticles lies in the range of 30-55 nm. Mossbauer spectroscopy was employed to probe magnetic properties at microscopic level. Mossbauer analysis indicates that dopant ions largely prefer 12k, 4f(1) and 2b sites at x=0.2 and 0.4 levels whereas at higher concentrations substitution Lakes place at 12k and 4f(2) sites. Magnetic measurements reveal that the values of coercivity (H-c) reduced from 6082 (x=0) to 1104 Oe (x=1.0) but the net magnetization of the samples is not correlated with dopant level. The saturation magnetization (M-s) values are in the range of 64.8-56.8 emu/g. Our results suggest that magnetization and magneto-crystalline anisotropy are closely related to the distribution of Co-Zr on the five sublattices of the crystal. (C) 2014 Published by Elsevier B.V.