Magnetic Susceptibility and Permeability

Magnetic susceptibility is the amount of magnetisation that is generated when exposed to a unit-strength magnet. Magnetic permeability is the correlation of magnetic induction to the magnetic intensity of a material. Magnetic permeability is a scalar quantity, and its symbol is ‘μ’. 

Magnetic permeability aids in measuring a material’s resistance to the magnetic field, or in other words, it is the measurement of the degree to which the applied magnetic field can potentially penetrate a material.

The magnetic conductivity will be higher if a material has bigger magnetic permeability. 

The magnetic permeability helps the magnetic force of lines pass through a substance. 

Magnetic Susceptibility

Magnetic susceptibility is an electromagnetic characteristic of a material that indicates how strongly it is magnetised. When a magnetic field induces magnetisation in a material, the magnetic susceptibility, a dimensionless proportionality factor that indicates the degree of magnetisation, is measured. The magnitude of M is comparable to the applied field in the following statement:

Magnetic susceptibility formula:

Xm = M/H

XM: magnetic susceptibility

M: magnetisation

H: applied magnetising field intensity

A magnetic susceptibility ratio does not have a unit because it is the ratio of two quantities expressed in the same units. Magnetic susceptibility is affected by material and temperature characteristics.

The Mathematical Term

In this case, Xm = I if H =M.

In other words, a material’s magnetic susceptibility is the amount of magnetization it generates when exposed to a unit-strength magnet.

According to the magnetic permeability, materials can be classified as follows:

• Diamagnetic materials – When placed in a magnetic field, diamagnetic materials are easily magnetised. In simple terms, these materials are repelled by a magnetic field. All the materials containing atoms that have paired electrons show diamagnetic properties. An example of a diamagnetic material is Bismuth.
• Paramagnetic materials – When placed in a magnetic field, paramagnetic materials tend to become weakly magnetised in the direction of the magnetising field. However, when the applied field is removed, the materials lose their magnetism. This is because thermal motion causes the electrons’ spin orientations to be randomised. 

Environmental Effects of Magnetic Susceptibility 

The temperature-dependent properties of most materials necessitate equilibration of cores to ambient temperature. For paramagnetic materials, (Paramagnetic materials have permanent atomic dipoles. They act individually and range in the direction of the external magnetic field.), the Curie-Weiss equation states that k = c/T, with c being the Curie constant and T being Kelvin temperatures. At 20°C, the MS of pure paramagnetic material is 1.7 percent (3.5 percent; 7.1 percent) greater than the room temperature susceptibility at 5°C (10°C; 20°C) below room temperature. Between 0°C and 20°C, other materials’ temperature dependence is less pronounced.

Since the magnetic field aligns the paramagnetic molecules’ magnetic moments somewhat, the magnetic susceptibility of a compartment containing Gd-DTPA chelates changes. The shape and orientation of the magnetic field in which the host molecule resides also play a role in this shift in susceptibility. The water protons’ local magnetic fields are modified by the magnetic susceptibility differential, which has an effect on the local resonance frequencies. 

Characteristics of Magnetic Susceptibility

It is possible to predict a material’s behaviour by its magnetic susceptibility. By using this technique, a magnetic field’s ability to attract or repel a material can be studied. When paramagnetic materials discover places with higher magnetic fields, they might be drawn to them. While aligned with the magnetic field, this is what happens. Depending on the situation, diamagnetic materials (Diamagnetic materials are those that lack properties of permanent magnetisation without the external magnetic field) may exhibit unique behaviour. Magnetic fields cannot be aligned in these materials. As a result, materials are pushed away from higher magnetic fields and towards regions with lower ones. The magnetisation of the material is always above the applied field. It is added to the magnetic field that it already has. It can alter paramagnetism and diamagnetism using different types of field lines. It is possible to quantitatively measure magnetic susceptibility. All of them can provide us with the necessary insights based on material structure. Besides that, they can reveal information about the material’s energy levels and the strength of their bonds.

Magnetic Permeability

The formula for magnetic permeability is given as:

Magnetic Permeability (μ) = B/H

B = magnetic intensity

H = magnetising field

It is measured in Henries per metre (h/m) or newtons per metre squared.

Applications of Magnetic Permeability

• Generation, distribution and conversion of energy
• Storage and retrieval of information
• Media and telecommunications
• Magnetic compasses
• Electric generators
• Magnetic tape
• Characterisation of magnetic materials

Relation Between Magnetic Permeability and Magnetic Susceptibility

The relation is established as follows:

Taking relevant equations for the relationship to form.

B = μ0(H+M) and M = XmH

B = μ0(H+XmH)

B = μ0H(1+Xm)

So,

μH = μ0H(1+Xm)

μ/μ0 = μr

Xm = 1 – μr

Conclusion

We have learned that magnetic susceptibility and permeability is a material attribute that defines how the magnetic field inside a material changes compared to the magnetisation field in which it is placed. In other words, it shows how easily a generated magnetic field affects a substance. This material property’s application is extremely important in a variety of sectors. Materials with extremely high magnetic permeability are used in electromagnets, transformers, and inductors.