Susceptibility in Physics
Magnetic susceptibility is a proportionality constant. It has no dimension. The term is associated with many things in Physics.
Susceptibility meaning in physics signifies the total amount of magnetization of material at the same time when a magnetic field is applied. This phenomenon is due to the interactions of electrons and nuclei.Β
It happens when both the nuclei and the electrons are applied externally under the magnetic field. The magnetic susceptibility is nothing but the total amount of magnetization of a material when it undergoes a magnetic field.Β
This article is all about susceptibility Physics and other stuff associated with susceptibility.
Susceptibility of Magnetic Material
From the introduction, you can gain basic ideas about magnetic susceptibility meaning. Magnetic susceptibility helps in the measurement of the amount of magnetization when it comes under the applied magnetic field.
Do you know the value of magnetic susceptibility?
The formula that can be helpful for the calculation of magnetic susceptibility values is:
Ο = M/H
Here,
Ο = Magnetic susceptibility
H = field intensity
M = magnetization
Various Types of Magnets
1. Paramagnetic MaterialΒ
Paramagnetic materials are the type of objects (Magnetic materials) that lies within (align with) the magnetic field. The value of Magnetic susceptibility is Ο > 0 in the case of paramagnetic materials. This expression has some sort of expression.Β
When you try to determine the values for paramagnetic materials, they always give you a small positive value.Β
Paramagnetic materials are having different dependencies. The temperature of each paramagnetic material is a dependent quantity. The rise of temperature in paramagnetic materials can lessen the magnetic field.Β
These types of materials have relative permeability that varies from 1.00001 to 1.003. A few examples of paramagnetic materials are given below:Β
Alkaline earth metal
Aluminum
OxygenΒ
Curieβs law is available to calculate the magnetization of the paramagnetic materials. So, the magnetization formula according to Curieβs law can be written as:
M = Ο H = {C / T x H}
Where,
M = magnetization
C = material-specific Curie constant
Ο = magnetic susceptibility
H = auxiliary magnetic field
T = absolute (Kelvin) temperature
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2. Diamagnetic Material
Diamagnetic materials are the types of Magnetic materials that line up alongside the magnetic field. The value of magnetic susceptibility for diamagnetic materials is Ο<0. The relation signifies that for diamagnetic material, the value of magnetic susceptibility is always a negative one.Β
The magnets do not attract these materials but prefer to repel. The magnetic field of the diamagnetic material travels from a stronger field to a weaker field. Diamagnetic materials are not dependent on temperature.Β
Diamagnetic materials have magnetization that acts in the opposite direction. magnetization intensity of the diamagnetic materials lies within a definite value. Relative permeability does not vary at all for every Diamagnetic material. Examples of Diamagnetic materials are:Β
GoldΒ
TinΒ
MercuryΒ
WaterΒ
CopperΒ
ZincΒ
BismuthΒ
SilverΒ
Antimony
MarbleΒ
GlassΒ
NaCl, etc.
Here is the table for Diamagnetic Materials and the value of their volume susceptibility:
3. Ferromagnetic Material
Ferromagnetic materials are the types of magnets that can possess higher magnetization when present in a magnetic field. The attraction force of the magnets for the ferromagnetic materials is very high. The magnetic field of the ferromagnetic materials always come from weaker fields to stronger fields.Β
You wonβt find any constant relative permeability for ferromagnetic materials.Β The value of relative permeability varies from 1,000 to 1,00,000. You also find a very high and positive magnetic susceptibility among ferromagnetic materials.
The magnetic susceptibility Physics relies on the applied field. A few examples of ferromagnetic materials areΒ
IronΒ
CobaltΒ
Nickel (and their alloys)
Interesting Facts on Magnetic susceptibility
The magnetic susceptibility can indicate the behavior of a material. It can elaborate whether a material can get attracted or repelled out within the magnetic field. Paramagnetic materials can be attracted by the magnetic field when they find the regions that have greater magnetic fields. This happens when they align with the applied magnetic field.Β
In different scenarios, you may find some unusual behavior with the diamagnetic materials. These types of materials do not support the alignment of magnetic fields. As a result of which, each material gets a push-away towards the regions of lower magnetic fields.Β
The magnetization of the material is always on the top of the applied field. It is added to its original magnetic field. It can create different types of field lines to manipulate under paramagnetism or get the exclusion for diamagnetism.
Magnetic susceptibility values can have some sort of Quantitative measures. All of them can give us the proper insights that are based on the structure of materials. Also, it can provide insight into energy levels and the bonding of the materials.Β
FAQs on Magnetic Susceptibility
1. What is magnetic susceptibility in Physics?
Magnetic susceptibility, represented by the symbol π (chi), is a fundamental property that measures how much a material will become magnetised when placed in an external magnetic field. It quantifies the degree of magnetisation a material acquires in response to an applied field. A positive value indicates attraction, while a negative value indicates repulsion.
2. What is the formula to calculate magnetic susceptibility?
The formula for magnetic susceptibility (π) is defined as the ratio of the intensity of magnetisation (M) induced within the material to the applied magnetic field intensity (H). The equation is: π = M / H.
3. What is the SI unit and symbol for magnetic susceptibility?
The standard symbol for magnetic susceptibility is the Greek letter chi (π). Since it is the ratio of two quantities (M and H) that have the same unit (Amperes per metre), their units cancel out. Therefore, magnetic susceptibility is a dimensionless quantity and has no SI units.
4. How are magnetic susceptibility (π) and relative magnetic permeability (ΞΌr) related?
Magnetic susceptibility and relative magnetic permeability are directly related concepts that describe a material's response to a magnetic field. The precise relationship, as per the CBSE 2025-26 syllabus, is given by the formula: ΞΌα΅£ = 1 + π. This shows how permeability, which measures the total magnetic field inside a material, depends on the material's inherent susceptibility to being magnetised.
5. How is magnetic susceptibility used to classify different types of magnetic materials?
The sign and magnitude of magnetic susceptibility (π) are used to classify materials into three main categories:
- Diamagnetic Materials: These have a small, negative susceptibility (π < 0), meaning they are weakly repelled by magnetic fields. Examples include copper, water, and gold.
- Paramagnetic Materials: These have a small, positive susceptibility (π > 0), meaning they are weakly attracted to magnetic fields. Examples include aluminium and oxygen.
- Ferromagnetic Materials: These have a large, positive susceptibility (π >> 1), indicating they can be strongly magnetised. Examples include iron, cobalt, and nickel.
6. Why is the magnetic susceptibility of diamagnetic materials negative?
The magnetic susceptibility of diamagnetic materials is negative because when placed in an external magnetic field, a magnetic moment is induced in the opposite direction to the applied field. In accordance with Lenz's Law, this induced field opposes the external field, causing a weak repulsive force. This fundamental opposition results in a negative value for susceptibility.
7. How does temperature affect the magnetic susceptibility of paramagnetic materials?
For paramagnetic materials, magnetic susceptibility is inversely proportional to the absolute temperature (T). This relationship is described by Curie's Law, which states that π = C / T, where C is the material-specific Curie constant. As temperature rises, thermal agitation increases, disrupting the alignment of atomic magnetic dipoles with the external field and thereby reducing the material's susceptibility.
8. Why is soft iron a preferred material for making the cores of electromagnets?
Soft iron is ideal for electromagnet cores because of two key properties related to susceptibility and retentivity. It possesses a very high magnetic susceptibility, allowing it to become strongly magnetised in a weak field. Crucially, it also has low retentivity, meaning it demagnetises almost completely when the current is turned off. This combination creates a powerful and easily controllable temporary magnet.
9. What is the fundamental difference between retentivity and magnetic susceptibility?
The key difference lies in what they measure in a material's magnetic life cycle:
- Magnetic Susceptibility (π) measures a material's ability to become magnetised when an external magnetic field is present. It reflects how easily the material responds to the field.
- Retentivity measures a material's ability to stay magnetised after the external magnetic field is removed. It reflects the material's magnetic 'memory'.
10. Why is water, a common substance, considered a diamagnetic material?
Water (HβO) is diamagnetic because its molecules lack permanent magnetic dipole moments. When subjected to an external magnetic field, the orbital motion of electrons within the molecules is slightly altered. This change induces a new, weak magnetic field that opposes the external field, leading to a gentle repulsion. This repulsive behaviour is the defining characteristic of diamagnetism, resulting in a small negative magnetic susceptibility.
