Ferromagnetic materials – examples, origin & properties

In another article, we have discussed that most of the materials are affected by the magnetic field. These materials are the magnetic materials. These materials can show the magnetic properties. The origin of magnetic moment in these materials is the rotation of orbital electrons around the nucleus. On the basis of magnetic properties of materials there are five types of magnetic materials – Diamagnetic materials, Paramagnetic materials, Ferromagnetic materials, Ferrimagnetic materials and anti-ferromagnetic materials. In this article, we are going to discuss origin, properties and examples of ferromagnetic materials.

Contents in this article:

  • What are ferromagnetic materials?
  • Example of ferromagnetic material
  • Origin of ferromagnetism
  • Properties of ferromagnetic material
  • Uses of ferromagnetic material

What are ferromagnetic materials?

Ferromagnetic material is the type of material that is attracted strongly by external magnetic field. One can convert a ferromagnetic material like iron rod, steel into a permanent magnet by the process of magnetic induction. This type of materials can retain the induced magnetism even after removing the external magnetic field.

Examples of ferromagnetic materials

Iron (Fe), Nickel (Ni), Cobalt (Co), Gadolinium (Gd) and some alloys like steel etc. are the most common 5 examples of ferromagnetic materials. If someone ask you for the examples of magnetic materials, you should give the examples of ferromagnetic materials. This type of magnetic materials has significant amount of magnetic properties.

Origin of ferromagnetism

Ferromagnetic materials have high magnetization. Such high value of magnetization is not due to spin of electrons only. There is something else. This can be explained by domain theory.

Scientists think that this type of materials have large number of domains inside these. All the atomic dipoles in a domain have same orientations but the dipole moments of different domains have different orientations. Therefore, the net dipole moment is non-zero for each domain individually. But the net dipole moment of entire material becomes zero as the overall dipole moment of all domains cancels each other. In the diagram, there are four domains and the orange colored arrows represent the dipole moments in each domain.

Domains in Ferromagnetic materials
Domains in Ferromagnetic materials before applied field

Now, if the material is placed in external magnetizing field, dipoles of all domains try to orient in the direction of applied magnetic field. At this, the resultant dipole moment becomes very high. Hence, its magnetic property appears which is much stronger than the diamagnetic property. On increasing the strength of magnetizing field, ferromagnetic material becomes more magnetized. But after a certain limit it reaches to the saturation level where the magnetization of ferromagnetic material will not increase even after increasing the external field.

Properties of ferromagnetic materials

Magnetic field lines inside a Ferromagnetic material
Magnetic field lines inside a Ferromagnetic material are more denser

Here is the list of some properties of ferromagnetic materials –

  1. Attracted strongly by the magnet.
  2. Magnetic field lines are more denser inside this material when it is in external magnetic field.
  3. Relative magnetic permeability is very high (in the order of 102 to 106).
  4. Magnetic susceptibility is much greater than unity.
  5. Ferromagnetic material shows hysteresis property.
  6. This type of materials can retain the magnetic property even after removing external magnetic field. So, one can use a ferromagnetic material as a permanent magnet after the magnetic induction.
  7. After a certain temperature this type of materials behave like paramagnetic materials. This critical temperature is the Curie’s temperature.

Uses of ferromagnetic material

  1. Ferromagnetic material is used in core of transformer.
  2. One can convert these type of materials into permanent magnets.
  3. Ferromagnetic material is also used in dynamo and motor.

Some Important questions on ferromagnetic material

1. What is Curie’s temperature?

Ans: Curie temperature is the critical temperature of a ferromagnetic material above which it behaves like a paramagnetic material.

2. What is the value of relative permeability in ferromagnetic material?

Ans: Relative magnetic permeability for a ferromagnetic material is very high and usually it has the value in the order of 102 to 106.

This is all from this article on properties and examples of ferromagnetic materials. If you have any doubt on this topic you can ask me in the comment section.

Thank you!

Related posts:

  1. Magnetic and non-magnetic materials – definition, examples and differences

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