Ferromagnetic materials are materials that exhibit strong magnetism in the same direction as an applied magnetic field and retain their magnetic properties even after the external field is removed. This type of material includes elements like iron, nickel, cobalt, and some of their alloys. Ferromagnetism is due to the alignment of magnetic moments within the material, which results from interactions among the atomic dipoles that tend to align parallel to each other.
Magnetization Process
To understand the process of magnetization of the core, a ferromagnetic material can be considered to be composed of small areas called “magnetic domains”. Magnetic domains are like very small magnets, which are randomly oriented, to assume minimum-energy state.
In the presence of a source of mmf, such as a coil of turns of wire carrying a current , wrapped around one arm of the core of a magnetic circuit, the magnetic domains tend to align themselves with the magnetic field produced by the coil, resulting in an increase in the magnetic field density. A
s the current is increased, the alignment continues till all magnetic domains are aligned with the external magnetic field. At this point, the core is said to be saturated and increasing the applied mmf will not result in any increase in the magnetic field density produced.