What is Magnetic Hysteresis

What is Magnetic Hysteresis

• When the exterior magnetic field is provided to the ferromagnetic substance like iron, the dipoles of different iron's atom arrange themselves with the direction of the applied magnetic field this fact is known as magnetic hysteresis.

• When we eliminate the field around the iron material it still shows magnetic properties due to the alignments of the domains of the iron.
• To extract the residual magnetic properties, there is a need of some heat or magnetic field is provided with different polarity.
• The graphical representation among the magnetic field intensity H and magnetization M of the ferromagnetic material is shown in a given figure.
• You can see from the figure that the magnetization of the material increases first then it get saturated and there is no further increase in with the field intensity increment.
• When we demagnetize the magnetic element its magnetization curve does not follow the field intensity H, but it has some value when the external field is zero.
• This feature of the material to have some amount of the magnetization is known as the remanence.
• The curve constituted by association of the magnetization M and field intensity H is recognized as the hysteresis loop. The area of the loop depends on the magnetization material in case of the iron it will be larger.
• If you see the given curve you will observe that it is not linear but there are a lot of turns in the curve that called Barkhausen jumps (it is a line to which the curve meets).

  

Magnetization and Field Intensity Curve

• In the given diagram, the magnetization and field intensity curve of the steel and iron is drawn.
• We can observe from the figure that the magnetization of the materials increases with the increment of the field intensity after some time the increment in the flux density decreases while still, the intensity of the field is increasing.

• It is because all domains of the materials have become aligned with the external field, so there is no further increase in the magnetization of the substance this point at the curve is known as the saturation region.

  

Retentivity

• For the explanation, suppose that we have a wire of the iron and it is connected with the battery and all the domains are aligned with the external field and the conductor is fully magnetized.
• Now if we remove the external power source from the conductor, then the iron should be totally demagnetized, but it did not happen.
• It is due to some residual magnetization of the material, this property of any material to have some magnetization when it is not connected with the battery is known as the retentivity.
• The reason for this is that some domains of the wire are still magnetized instead of the removal of the battery from the terminals of the conductive wire.
• The amount of retentivity is different for the different materials like steel gets demagnetized very soon but in the case of iron, its value is higher.
• To magnetize any material we need to provide the magnetic field intensity with the opposite polarity.
• The force provided by the opposite polarity magnetic field is known as the coercive force.

Soft Magnetic Material

• When we removed the external field from any conductor then it still has some magnetization properties the value of the magnetization is different for different materials. To demagnetize the substance we provide the external field with opposite polarity.
• The amount of the force need to demagnetize is known as the hysteresis loos.
• The value of this energy is different for different materials like in steel its value is less so it called soft magnetic materials.
• The curve for these materials has less area.

  

Hard Magnetic Materials

• There is another type of materials that required a large amount of the energy for demagnetization and have larger area are known as the hard magnetic materials.
• The coercive force of these materials is larger than the soft magnetic material.

• The energy required for the demagnetization of these materials is larger than the soft materials.
• The curve for these materials is shown in the given figure.

  

Applications of the Magnetic Hysteresis

• These are some applications of the magnetic hysteresis
• Mostly motor driver circuits are constructed by the hard magnetic materials.
• Speakes, tape recorders are made by such materials that have higher magnetic properties.
• Our personals computers are also used for magnetic substances.
• Different electronic instruments like energy meter, sensing devices also used hard magnetic materials.
• In medical devices like MRI also used hard magnetic substances.
• Soft magnetic material is used in the transformer core because they can easily magnetize and demagnetized.