# Magnetic Susceptibility

Magnetic susceptibility is a dimensionless proportionality constant that indicates the degree of magnetization of a material in response to an applied magnetic field. It is caused by interactions of electrons and nuclei with the externally applied magnetic field.

## What is Magnetic Susceptibility?

In electromagnetism, magnetic susceptibility is defined as:

The measures of how much a material will be magnetized in an applied magnetic field.

It is denoted by χ.

### Magnetic Susceptibility Formula

The mathematical definition of magnetic susceptibility is the ratio of magnetization to applied magnetizing field intensity. This is a dimensionless quantity.

 $\chi =M/H$

Where,

• χ: magnetic susceptibility
• M: magnetization
• H: field intensity

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## Types of Magnets

With the help of magnetic susceptibility, magnetic materials can be classified as:

• Paramagnetic material: Magnetic materials which align with the magnetic field are known as paramagnetic materials. Magnetic susceptibility is χ>0 which means it is always a small positive value for paramagnetic materials. These materials are temperature dependent and are weekly attracted by magnets with relative permeability 1.00001 to 1.003. Alkaline earth metal, aluminium, oxygen etc are some of the examples of paramagnetic materials.
• Diamagnetic material: Magnetic materials which align against the magnetic field are known as diamagnetic materials. Magnetic susceptibility is χ<0 which means it is always a negative value for diamagnetic material. These materials are repelled by the magnets and they move from a stronger field to a weaker field. These materials are independent of temperature. As these materials magnetize in the opposite direction, they do have a small amount of magnetization intensity. Gold, tin, mercury, water, etc are examples of diamagnetic materials. Diamagnetic materials have a constant relative permeability.
• Ferromagnetic material: Magnetic materials that are highly magnetized in a magnetic field are known as ferromagnetic materials. These are highly attracted by the magnets and move from weaker fields to stronger fields. Ferromagnetic materials do not have a constant relative permeability and vary from 1000 to 100000. Magnetic susceptibility is very high and positive and depends on the applied field. Iron, cobalt, nickel and their alloys are examples of ferromagnetic materials.