# What is Magnetic Susceptibility?

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What is magnetic susceptibility? before I explain magnetic susceptibility definition, we need to know some terms such as magnetic field (H), magnetic flux density (B) and magnetic permeability (µ) Magnetic field : Lines of force will be produced which diffuses through the medium where the field is applied. Is magnetic susceptibility definition related to them?

Magnetic flux density is the amount of lines of force per unit area. Magnetic permeability: It means the connection between the magnetic field and magnetic flux density. (B = µH).

# What is Magnetic Susceptibility?

Now, Magnetic susceptibility can be simply defined as the measurement of the extent to which a substance can be magnetised by applying a peripheral magnetic field. It is denoted by (from the Greek letter chi). It can be measured as:

Where:

• M – magnetisation of the material
• H – Applied peripheral magnetic field strength

Now, we can know magnetic susceptibility definition that magnetic susceptibility is actually caused by the proportional activity of electrons and nuclei by the utilization of fringe magnetic field.

That is, a c happens inside it that will either restricts or increase the connected fringe field. If it restricts the connected magnetic field, the result will be diamagnetism.

If it intensifies the field (the electrons and nuclei which rotates in the same direction of magnetic field) it results in paramagnetic or ferromagnetic or super magnetism relying upon the level of strengthening.

The range of the value of magnetic susceptibility () of different magnetic substances is:

• Diamagnetic substances : < 0
• Paramagnetic substances : 1 > > 0
• Super paramagnetic and ferromagnetic substances : >> 1

Now, consider a material having magnetisation M which is placed under a peripheral magnetic field of B0 and the magnetic permeability of free space is µ0. Then, the total magnetic field in the material after applying peripheral magnetic field is given by:

When the internal magnetic field of the material is considered, µ0 can be substituted by µ which is given by µ = Km µ0. Where, Km is relative permeability.

If the material does not produce any internal magnetism with applied magnetic field, then the value of Km will be equal to 1. When Km>1, because of the use of a fringe magnetic field the material is magnetised. The can be connected with Km, i.e is defined as how much value the relative porousness varies from one.

m and Km will give same information. Both quantities are dimensionless.

## Magnetic Susceptibility and Temperature

The paramagnetic material will be in its magnetic state only when it is above a specific temperature. This particular temperature is called Curie temperature. The connection of same with magnetic susceptibility is explained by Curie law which is given by:

Where:

C – Curie constant.

T – Temperature in Kelvin.

The paramagnetic material with weak interactive electrons has to obey the Curie-Weiss law which is given by:

Where:

m – Molar magnetic susceptibility

θ – Weiss constant

The Curie-Weiss plot can be obtained by plotting a graph of 1/ m verses temperature. From that graph, we will get the curie constant by the inverting the slope and Weiss constant can be obtained from the y-intercept (Figure 1). If the Curie-Weiss law is fulfilled then the plot should be linear.