Effect of non-magnetic and magnetic trivalent ion substitutions on BaM-ferrite properties synthesized by hydrothermal method

Two spices trivalent transition metal ions, nonmagnetic Al 3+ , Bi3+ and magnetic Cr3+, Mn3+ substituted barium hexaferrite powders are synthesised via dynamic hydrothermal method then calcinated at different temperatures. Powder XRD patterns analysis and Rietveld refinement indicate magnetoplumbite-type crystalline phase. The crystallite size calculated using Scherer's formula varies from 153 to 248 nm as it is affected by the ionic radius of trivalent metal ions and calcination temperatures. The morphological features show agglomerations of spherical-shaped particles with an average size of 400 ± 50 nm for BaBiFe11 O19 and hexagonal-shaped particles 1-2μm for the other substitutions. Magnetic studies show a ferromagnetic behaviour for all samples. The nonmagnetic Al3+, Bi3+ substituted materials have lower saturation magnetization Ms and remanence Mr than the magnetic substitutions Cr3+, n3+. These results reveal that Ms and Mr are related to the magnetic moment of each metallic ion and its distribution in the lattice. For magnetic substitution, Ms of manganese substitution (61.10 emu/g) is found higher than that of chromium (60.33 emu/g) since Mn3+ has a magnetic moment of 5μB greater than Cr3+ with 3μB. Coercivity Hc and maximum energy product (BH)max determined from M-H loops exhibit an increasing trend with calcination temperature as they are related to the crystallite size. Hc and (BH)max of BaMnFe11O19 are found maximum 0.426 T and 7.47 kJ.m-3, respectively.