The effect of BaTiO3 on the magnetic behavior of MnZn ferrites at frequencies > 5 MHz

Abstract

In this article an extensive study is presented on the effect of BaTiO3 on the high frequency performance of MnZn ferrite having a nominal composition Mn0.9Zn0.1Fe2.45O4. It is shown that BaTiO3 at an optimum concentration of 200 ppm wt. is a bulk dopant that dissolves in the spinel lattice leading to microstructures with smaller grain sizes, lower grain boundary resistivities and higher resonance frequencies. Despite an observed increase on the hysteresis losses, the main impact on the magnetic performance is the significant reduction of the high frequency resonance losses. In addition, no dependency has been observed on the particle size of BaTiO3 since nanoparticles produce the same effects as microparticles. Through exploitation of the beneficial effects of BaTiO3, MnZn ferrites with power losses of 195 kW m−3 (5 MHz, 10 mT, 100 °C) or 1125 kW m−3 (10 MHz, 10 mT 100 °C) and a relative initial permeability of 200 could be synthesized. These results belong to the best reported in literature and indicate that the application region of MnZn ferrites can be extended up to application frequencies traditionally dominated by other ferrite material families.