Enhanced magnetic domain relaxation frequency and low power losses in Zn²⁺ substituted manganese ferrites potential for high frequency applications

Nowadays electronic industries prerequisites magnetic materials, i.e., iron rich materials and their magnetic alloys. However, with the advent of high frequency applications, the standard techniques of reducing eddy current losses, using iron cores, were no longer efficient or cost effective. Current market trends of the switched mode power supplies industries required even low energy losses in power conversion with maintenance of adequate initial permeability. From the above point of view, in the present study we aimed at the production of Manganese–Zinc ferrites prepared via solution combustion method using mixture of fuels and achieved low loss, high saturation magnetization, high permeability, and high magnetic domain relaxation frequency. The as-synthesized Zn²⁺ substituted MnFe₂O₄ were characterized by X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The fractions of Mn²⁺, Zn²⁺ and Fe²⁺ cations occupying tetrahedral sites along with Fe occupying octahedral sites within the unit cell of all ferrite samples were estimated by Raman scattering spectroscopy. The magnetic domain relaxation was investigated by inductance spectroscopy (IS) and the observed magnetic domain relaxation frequency (f_r) was increased with the increase in grain size. The real and imaginary part of permeability (μ′ and μ″) increased with frequency and showed a maximum above 100 MHz. This can be explained on the basis of spin rotation and domain wall motion. The saturation magnetization (M_s), remnant magnetization (M_r) and magneton number (µ_B) decreased gradually with increasing Zn²⁺ concentration. The decrease in the saturation magnetization was discussed with Yafet–Kittel (Y–K) model. The Zn²⁺ concentration increases the relative number of ferric ions on the A sites, reduces the A–B interactions. The frequency dependent total power losses decreased as the zinc concentration increased. At 1 MHz, the total power loss (P_t) changed from 358 mW/cm³ for x=0–165 mW/cm³ for x=0.9. P_t for all the Zn doped samples exhibited the temperature stability up to 100 °C.