Effect of high energy milling on the synthesis temperature, magnetic and electrical properties of barium hexagonal ferrite

• BaFe12O19 hexagonal ferrite generates an immense interest in permanent magnetic applications due to its complex crystal structure, high coercivity, high retentivity and uniaxial anisotropy.
• The ball mill assisted ceramic method gently affects the magnetic and electrical properties.
• The size of the prepared nanoparticles suggests the single magnetic domain nature.
• The temperature dependent magnetization confirms the single domain nature with a sharp Hopkinson peak.
• Initial milling process creates non-traceable amount of oxygen vacancies which contribute to the electrical conduction process only at high temperature.
• The sample has high dielectric constant and low dielectric loss.

Nanoparticles of barium hexagonal ferrite (BaFe12O19) have been synthesized by initial high energy milling of the precursors and sintering subsequently. X-ray Diffraction pattern reveals the hexagonal phase with a crystallite size of 42 nm. Scanning Electron Micrograph (SEM) shows the size of nanoparticles to lie in the range of single domain particles. X-ray Photoelectron Spectroscopy (XPS) indicates Fe in +3 state and an associated surface peak indicates its presence at different environments. Vibrating Sample Magnetometer measurements (VSM) illustrate ferrimagnetism with high coercivity and non-saturation of hysteresis behavior up to 8500 Oe. The initial high energy milling confines the particle size to the nanoscale which leads to high coercivity. Temperature dependent magnetization shows a sharp peak before transition which is the characteristic of the single domain magnetic behavior. Resistivity plot shows a decreasing trend with temperature. Two thermal activation energy values of 0.81 eV and 0.29 eV indicate the existence of two different conduction processes. The frequency dependent dielectric constant plot shows a semiconducting behavior. The dielectric loss plot shows a drastic change at high temperature due to the anion vacancies in addition to four types of polarization.