Microstructure dependence of AC magnetic properties in Mn-Zn ferrites

A correlation between microstructure and frequency dependent magnetic properties of Mn-Zn ferrites was established using the inductance spectroscopy method. Several atmosphere conditions and dwell times and temperatures were used during sintering to obtain a variety of microstructures in samples of different compositions. Results show that initial permeability (μ_i) strongly depends on the atmosphere composition during sintering, it increases, while relaxation frequency (f_r) slightly decreases as oxygen content decreases. On the other hand, dwell times longer than three hours led to a slight decrease in permeability (μ) and an increase in f_r. For the compositions prepared, a systematic decrease in μ was observed as zinc content decreases, regardless of the sintering conditions used. For each composition a maximum in μ was obtained for the same sintering conditions, which also correspond to the highest density values