Temperature dependent magnetic and dielectric properties of M-type hexagonal BaFe12O19 nanoparticles

• Published in: Journal of alloys and compounds 2012-12, Vol.545, p.225-230
• Main Authors: Krishna murthy, J., Mitra, C., Ram, S., Venimadhav, A.
• Format: Article
• Language: English
• Subjects: Activation; Barium compounds; Barium ferrite; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric loss and relaxation; Dielectric properties; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Exact sciences and technology; Ferrites; Magnetic and dielectric studies; Magnetic properties and materials; Magnetic properties of nanostructures; Magnetization; Nanoparticles; Oxygen vacancies; Physics; Saturation (magnetic); Scanning electron microscopy; Sol–gel processes
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.07.133

► BaFe12O19 nanoparticles were synthesized by sol–gel method and compared with the commercial bulk samples. ► Magnetic and dielectric studies up to low temperature have been reported. ► Nanoparticles show superior magnetic and dielectric permittivity over bulk counterpart. We report magnetic and dielectric properties of phase pure M-type barium ferrite nanoparticles of size ∼90nm prepared by sol–gel method and were compared with a commercially available bulk powder. X-ray diffraction and field emission scanning electron microscope studies revealed a P63/mmc hexagonal crystal structure with plate shaped particles. Magnetization of commercial sample showed saturation magnetization close to theoretical value. The nanoparticles exhibited a saturation magnetization (Ms)∼70emu/g with a large coercive field Hc∼5320Oe at room temperature. At low temperatures, M (T) and M (H) loops revealed a decrease in zero field cooled magnetization below ∼50K, sharp rise in Hc and non-saturation of Ms; presence of defects on the surface can promote such changes in the magnetization behavior. Temperature and frequency dependent dielectric properties of the nanoparticles exhibited multiple relaxations with thermal activation behavior and high dielectric loss. Impedance analysis revealed a large value of dielectric permittivity that can be attributed to Maxwell–Wagner relaxation originating from the grain boundaries.