Although there are many types of magnetic materials and alloys, there are three main classifications of materials commonly used in the construction of power inductors. They are: Soft, Semi-Hard and Hard. These classifications characterize a material’s ability to absorb magnetic energy without retaining it. Soft magnetic materials multiply the magnetic field strength that an inductor generates and then return to a non-magnetized state when the flow of current through the coil stops. This effect is very desirable for power electronics applications and is why magnetically “soft” materials are used extensively in power inductor constructions as well as in most power electronics components. Soft materials can be further classified into two types, one being - Ferrimagnetic materials, which are soft magnetic materials composed of ferrite (which has a very high magnetic permeability) and two being - and Ferromagnetic materials, which include, but are not limited to, the materials listed in this slide and a wide variety of alloys composed of these elements. “Hard” materials are very useful as magnets; after coming into contact with a magnetic field, they can retain a strong magnetic field even after the source of the magnetizing force is removed. However, this effect is not useful for power electronics applications.