Magnetic core refers to a sintered magnetic metal oxide composed of various iron oxide mixtures. For example, manganese-zinc ferrite and nickel-zinc ferrite are typical magnetic core materials. Manganese-zinc ferrites are characterized by high magnetic permeability and high magnetic flux density with low loss characteristics. Nickel-zinc ferrites have extremely high resistivity and low magnetic permeability of less than a few hundred. Ferrite cores are used in coils and transformers of various electronic devices.