Sol–gel synthesis, structural and magnetic properties of nanoscale M-type barium hexaferrites BaCo_xZr_xFe_(12-2x)O₁₉

Abstract

We have accomplished a low temperature sol–gel synthesis of nanocrystalline M-type hexaferrites BaCo_xZr_xFe_(12-2x)O₁₉ (x=0, 0.2, 0.4, 0.6, 0.8 and 1.0). These compounds were characterized by TGA–DTA, FT-IR, XRD, EDS and TEM. X-ray diffraction patterns demonstrate that the compounds are single phase M-type barium hexagonal ferrites (BHF) and maximum substitution is attained at x=1.0. The average size of the hexagonal platelets is 41.62 nm. MS is employed to probe the magnetic properties at microscopic levels. MS studies suggest that both the nature and concentration of dopant ions control site preferences in the crystal lattice. Substitution is preferred at 4f₂ and 2b sites at x=0.4, 4f₁ and 4f₂ sites at x=0.6 and 2a and 2b sites at x=1.0 levels. M vs H studies reveal that on substitution M_S vary only slightly from 63.63 to 56.94 emu/g while a drastic reduction has been observed in H_C from 5428 to 630 Oe. High M_S and low H_C values of these materials make them particularly suitable for application in data recording. Our results also show that H_C can be monitored independently while retaining high saturation magnetization of BHF by making coupled substitution of divalent (Co²⁺) and tetravalent (Zr⁴⁺) cations for Fe3+ ions.