Magnetic Intensity and Magnetisation

In any magnetic field, magnetisation is a vector number that measures the intensity of a persistent or induced dipole moment. Magnetic polarisation is another name for magnetisation. 

We’ve all played with magnets at some point during our childhood. Have you ever wondered what makes these magnets magnetic or the relationship between magnetisation and magnetic intensity? And are the magnetic moment and magnetic dipole the same?

The arrangement of atoms within a substance determines a magnet’s magnetic behaviour. When a ferromagnetic substance is exposed to a strong external magnetic field, it is subjected to a torque, which causes the substance to align itself in the applied magnetic field and become strongly magnetised in that direction. With magnetisation, materials may be easily categorised based on their magnetic properties.

Magnetic intensity describes the forces that a magnet’s poles experience in a magnetic field. On the other hand, magnetisation intensity changes the magnet’s magnetic moment per unit volume.

Magnetic intensity and magnetisation

A bar magnet attracts iron objects to its poles, which are the magnet’s ends. At one end, the north pole is located, while the south pole is located at the other. The force exerted by magnets causes magnetism, which produces fields that attract or repel other metallic things. The density of magnetic dipole moments induced in a magnetic substance when located close to a magnet is known as magnetisation.

The magnetic effects can also be created by putting an electrical current through it; the magnetism effect is caused by electron mobility in atoms or the spinning of electrons or nuclei. Electrically charged particles cause it to happen. The quantity of charge, the particle’s velocity, and the strength of the field all influence the force exerted on electrically charged particles in a magnetic field. According to the laws of magnetism: 

• Same poles repel each other

• Opposing poles are attracted to one another

What is the source of magnetisation? 

Magnetisation is induced by a magnetic moment caused by the movement of electrons in an atom or by the spin of electrons. The response of that material to its external magnetic field is paired with the unbalanced magnetic dipole moment that was innate in that material due to electron mobility inside it to produce net magnetisation. Magnetisation helps in the identification of various materials based on their magnetic properties. It’s a quantity with a vector.

The formula of magnetisation:

I=Magnetic Moment/Volume

 I=M/V 

Magnetisation can be mathematically defined as:

M=m_net /V      

Where: m_net is the material’s magnetic moment, and V is its volume. 

The idea of magnetisation is further explained using the example of a solenoid.

Consider a case related to the solenoid with n turns per unit length. I represent the current that passes through it. The magnetic field inside a solenoid may be estimated using the following formula:

B₀= μ₀nI

If we load the solenoid with a non-zero magnetisation material, the field inside the solenoid must be larger than before. The net magnetic field B inside the solenoid can be expressed as:

B=B₀+B_m

in which: B_m = the core material’s magnetic field

B_m is proportional to the magnetisation of material M in this mentioned case, and it may be determined analytically as:

B_m=μ₀M

The constant permeability of the vacuum is denoted by μ₀.

We can extend this approach by introducing another vector field, H. The magnetic intensity of material is represented by the letter H. Magnetic intensity is that vector quantity that expresses a magnetic field’s strength at a specific location. The magnetic intensity of a given material can be calculated by: 

H=B/μ₀-M

A material’s total magnetic field can alternatively be computed as follows: 

B=μ₀(H+M)

Where H denotes the magnetic field created by external causes; (e.g. current in solenoid) 

Due to the core’s nature, M stands for the magnetic field.

The core’s nature in the above formula is determined by external forces and can be computed using the following formula:

M=χH 

The magnetic susceptibility of the material, also known as χ, describes how any magnetic material reacts to the external field and is defined here. It is an irrational amount.

Varying materials have different magnetic susceptibilities. It is tiny and positive for paramagnetic materials, while for diamagnetic, it’s negative and small. It can be calculated using the following formula:

B = μ₀(1+χ)H

= μ₀μ_rH

 = μH

Magnetisation, also known as magnetic polarisation, is a vector number that describes the frequency of persistent or induced dipole moments in a magnetic material. Magnetisation is caused by the magnetic moment caused by the mobility of electrons in atoms or, to put it another way, the spin of nuclei or electrons.

Net magnetisation is claimed to occur from a material’s response to an external magnetic field and any imbalanced magnetic dipole moment that is usually present in the material due to the motion of its electron, as previously stated.

This article discussed magnetic intensity and magnetisation, the formula of magnetisation and magnetic intensity, and the definition of magnetisation and magnetic intensity.

Conclusion

The magnetic behaviour of a magnet is characterized by the alignment of the atoms inside a substance. When a ferromagnetic substance is brought under the application of a strong external magnetic field, then they experience a torque wherein the substance aligns themselves in the direction of the magnetic field applied and hence gets strongly magnetized in the direction of the magnetic field. The magnetic intensity defines the forces that the poles of a magnet experiences in a magnetic field whereas the intensity of magnetisation explains the change in the magnetic moment of a magnet per unit volume.