Ferrites are polycrystalline oxides manufactured by ceramic technology and belong to a class of materials that exhibit the technically useful property of ferromagnetism. In a ferromagnetic material, magnetism occurs under the influence of an externally applied field. On removals of this field, material returns to its non-magnetic state. This behaviour is termed as magnetically "soft".
The general composition of these soft ferrites is MeFe2O4, where Me represents one or several of the divalent transition metals such as Manganese (Mn), Zinc (Zn), Nickel (Ni), Copper (Cu), Iron (Fe) or Magnesium (Mg), the most popular being Manganese-Zinc (Mn-Zn) and Nickel-Zinc (Ni-Zn) ferrites. These compounds exhibit good magnetic properties below a certain temperature called the Curie Temp (Tc). These materials can be used up to very high frequencies without laminating. Ni-Zn ferrites have a very high receptivity and are most suitable for frequencies over 1 MHz however Mn-Zn ferrites exhibit higher permeability and saturation induction levels and are suitable up to 3 MHz.