Crystal structure and magnetic properties of high Mn-doped strontium hexaferrite

We present a study on the effect of the substitution of Fe+3 by Mn+3 on the structural and magnetic properties of strontium hexaferrite, SrFe12-xMnxO19 (0 <= x <= 5), which is synthesized by assisted high-energy ball milling. A mechanism of substitution is proposed. Fe2O3, SrCO3 and Mn2O3 powders were mixed in a stoichiometric ratio, milled for 5 h and annealed at 950 degrees C for 2 h. The X-ray diffraction patterns confirm the formation of a hexaferrite structure with small amounts of Fe2O3 as a second phase for low doping levels of Mn3+ and reveal a modification of the lattice parameters as the rate of Mn3+ substitution increases. The magnetic properties demonstrate an important reduction of the magnetic saturation and a significant increase in the coercivity field with cation substitution. The M+ ossbauer results confirm that the Mn3+ ions preferentially occupy the 2a and 12k sites while avoiding the 2b site. (C) 2016 Elsevier B.V. All rights reserved.