Topical advances in synthesis for energy-efficient magnetoplumbite nanoferrites

Abstract

Next-generation magnetic devices will be planar, smaller, light weight, and will do well beyond the present state-of-the-art devices. For this to become a reality, advances in ferrite materials must first be realized. Due to superior coercivity and lower material and processing cost, magnetoplumbites are preferred over the other types of hard ferrites. Magnetoplumbites are important hexagonal ferrites with formula RFe12O19 where R may be barium (Ba), strontium (Sr) or lead (Pb). Energy losses are important issues in these magnetic materials. Although SrFe12O19 have many advantages, but to lower the energy losses we need to improve the resistivity by reducing eddy current losses. Sr-Ba nanoferrites have potential for next generation of energy-efficient magnetic devices. Gadolinium (Gd) belongs to the lanthanide series. In this work, Sr hexaferrites and Sr-Ba hexaferrites doped with rare earth metal like Gd were synthesized to increase their resistivity. Strontium barium hexaferrites with composition Sr1−xBaxFe12−yGdyO19 (x = 0.0, 0.25 and y = 0.0, 0.20) were synthesized by without water and surfactants (WOWS) sol–gel method and co-precipitation method, respectively. All the synthesized samples showed hexagonal structure with P63/mmc space group. Crystallite sizes obtained using Scherrer’s formula were in nanoregime. DC electrical properties as a function of temperature and dielectric spectroscopy as a function of frequency were evaluated and are correlated with the structural properties. A comparative study of different proportions of iron oxide and Gd dopant was carried out, and composition with x = 0.25 and y = 0.20 seems to be a suitable combination for high-frequency efficient devices.