Crystal Structure and Magnetic Properties of BaFe 12 x Dy x O 19 Powders Prepared using Gel Self-propagating Combustion

Abstract

The hexagonal BaFe₁₂ xDy_xO₁₉ (x ¹/4 0.1-0.5) powders are synthesized by the gel self-propagating combustion technique, which is combined with the sol-gel method and self-propagating combustion synthesis. The changes in heat and weight of dry gel during self-propagating combustion are investigated with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The effects of the molar ratio of citric acid on nitrates (C/N), calcination temperature, and substitution amount of Dy³⁺ on crystal structure and magnetic properties are studied by means of X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). In gel self-propagating combustion, the formation temperature of barium ferrite is decreased to 850 C. The changes in crystal structure during calcination are tracked. There is no α-Fe₂O₃ appearing in the powders when C/N is not less than 1.0. After some Fe³⁺ has been substituted with Dy³⁺, the magnetic properties are improved. The specific saturation magnetization reaches a maximum of 58.05 Am²/kg, and coercivity reaches a minimum of 420.33 kA/m with the substitution amount x ¹/4 0.2. This substituted barium ferrite can be used as a magnetic recording material.