A large domain wall pinning effect on the magnetic properties of ZrO2 added Mn–Zn ferrites

The effect of ZrO2 addition on the microstructure and magnetic properties of Mn–Zn ferrites was investigated. The results indicated that the initial permeability (μi), saturation induction (Bs) and power loss (PL) were significantly improved when the ZrO2 concentration was 0.02 wt%. A number of irregular particles were well dispersed on the surfaces of grains when the ZrO2 concentration exceeded 0.02 wt%. The irregular particles were considered to be agglomerated ZrO2 particles, and their precipitation process was observed. The pores along with ZrO2 particles on the surfaces of grains had a large pinning effect on the domain wall, which thus caused the decrease of magnetic properties. Non-magnetic Al element was detected, which indicates that a small amount of Al2O3 may dissolve in ZrO2. The optimal values of μi (2322), Bs (522 mT) and PL (386 kW/m3) were obtained, which shows a great promise for switched-mode power supply (SMPS) applications.