Types of Magnetic Material

Here I am just highlighting the various types of magnetic materials, not detailing which will help to understand the Electrical Machine and Measurement.

• Diamagnetic Material :-

What is a Diamagnetic Material :

• Definition -  The material which has no net magnetic moment without the presence of an external magnetic field(H).

Properties - 

• The magnetic field is non persistent that is magnetism only persist when an external field is applied.

       Non-Persistent means when you removed the magnetic field,                                           magnetic behavior goes away.

• Induced magnetic moment is small. (Like electric dipole moment, magnetism has magnetic dipole moment)
• Most important thing is that the direction of magnetization is in the opposite direction to the magnetic field.

       Explanation -  Before magnetic field is applied that means when H=0, the dipoles are oriented 

                         in random direction like as

                                                                        ↗↘←↑↙↓
                                                                        ↖←↙↗→

                                                                        →↑↓↖↘↙

             

                   But as soon as magnetic field is applied that means H≠0, then all dipoles get 

                   oriented in a direction opposite to applied magnetic field direction like as

                                                        ← ← ← ← ← ← ← ←

                        dipoles direction   ← ← ← ← ← ← ← ←

                                                        ← ← ← ← ← ← ← ←

                                                        ―――――――――→   H

                  The direction of magnetization is opposite to the direction of magnetic field 

                   because of orbital  motion of electron.

• So, Diamagnetic materials are repelled by magnetic field. - This is the property diamagnetic material.
• Example : Copper(Cu), Gold(Au), Germanium(Ge), Silicon(Si), Diamond.

• Paramagnetic Material

What is Paramagnetic Material ?

• Definition - The materials that are weakly attracted or magnetized by an externally applied magnetic field(H).

Properties -

• Same as Diamagnetic material that magnetism is non-persistent and weak magnetization.
• But the different is magnetic dipoles orientation, which are in the same direction of applied field(H).

Explanation -  Before magnetic field is applied that means when H=0, the dipoles are oriented in random direction like as

                                                                        ↗↘←↑↙↓
                                                                        ↖←↙↗→
                                                                        →↑↓↖↘↙

           

                   But as soon as magnetic field is applied that means H≠0, then all dipoles get oriented in the same direction to applied magnetic field direction like as

                                                        ← ← ← ← ← ← ← ←

                        dipoles direction   ← ← ← ← ← ← ← ←

                                                        ← ← ← ← ← ← ← ←

                                                 H   ←―――――――――   

                  This is the only difference between diamagnetic material and paramagnetic material.

• So, Paramagnetic materials are attracted by magnetic field. - This is the property diamagnetic material.
• If applied field is removed, the materials tend to lose their magnetism because of randomize changes of the spin orientation due to thermal motion.
• Example : Potassium(K), Oxygen(O₂), Tungsten(W), Aluminium, Manganese, Fe₂O₃, FeCl₂ etc.

• Ferromagnetic Material :-

What is Ferromagnetic Material ?

• Definition - The materials which exhibit spontaneous magnetization at the atomic level, even in the absence of external field.
• When the magnetic field is applied , all the dipoles are oriented in the direction of the magnetic field and it has strong magnetization that means it's strongly attracted by magnet.
• Spontaneous magnetization or the residual magnetism is present in the ferromagnetic material.
• Ferromagnetic material has permanent dipole moment present in the domain.
• The relative permeability(μr) is very large for ferromagnetic material and varies linearly with the vary of magnetizing field.

                                      Relative Permeability, μr = 1+Xₘ

• The intensity of magnetization(M) is very large and positive and varies linearly with the vary of magnetizing field. So Saturation of a material is depends on the nature of the material.
• The magnetic flux density(B) of material is large and positive that means inside the ferromagnetic material the field lines are more dense. 

                                    Magnetic flux density, B = μ₀(H+M)

       where μ₀= magnetic permeability in the air, H= Strength of the magnetic field

• The magnetic susceptibility(Xₘ) is also very large and positive .

                                                          Xₘ = M/H

In ferromagnetic material shows hysteresis characteristics that means on removal of the external magnetic field, the material doesn't get demagnetized totally. That's why when applying magnetic field(H) is zero but there will be some magnetic flux. 

• Examples : Iron, Cobalt, Nickel etc.

• Ferrimagnetic Material :-

What is Ferrimagnetic material ?

• Definition - The materials, containing one or more elements with iron, cobalt, nickel, and some alloys or compounds.
• Magnetic dipoles have unequal magnitude and after applying magnetic field the adjacent poles are oriented in opposite direction.

Explanation -  Before magnetic field is applied that means when H=0, the dipoles are oriented in random direction like as

                                                                        ↗↘←↑↙↓
                                                                        ↖←↙↗→
                                                                        →↑↓↖↘↙

           

                   But as soon as magnetic field is applied that means H≠0, then all dipoles get oriented in the opposite direction of each other and the net magnetic moment is small like as

               

        

                  The net magnetism is generally smaller as compare to the ferromagnetic material because adjacent dipoles are oriented in opposite direction.

• Ferrites are usually ferrimagnetic ceramic compounds which are derived from iron oxides. In household products such as refrigerator magnets  ferrites are used.
• Example:- Magnetite(Fe₃O₄), Jacobsite(MnFe₂O₄)