Magnetic Susceptibility: Formula and Types of Magnetic Material

Magnetic Susceptibility is a numerical measure of the ability of a material to be magnetised in response to a particular applied magnetic field. Mathematically, the ratio of the magnetization M within the material to the applied magnetic field strength H is known as the magnetic susceptibility of the material. Magnetization entails a particular amount of magnetism (dipole moment) per unit volume, this ratio is technically known as volume susceptibility.

Read More: Magnetic Field on the Axis of a Circular Current Loop

Key Terms: Magnets, Magnetic effect, Diamagnetic Material, Paramagnetic Materials, Magnetic field lines, Dipole moment, Magnetic field, Electromagnet, Magnetization

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Magnetic Susceptibility 

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• The degree of magnetization of a substance in response to an applied magnetic field is measured by magnetic susceptibility. 
• It is a dimensionless proportionality constant.
• Susceptibility refers to the overall quantity of magnetization that occurs at the same moment when a magnetic field is applied to a material. 
• Interactions between electrons and nuclei cause this phenomenon. 
• When both the nuclei and the electrons are externally applied under a magnetic field, susceptibility arises. 

Also Read: Moving Charges and Magnetism

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Magnetic Susceptibility Formula

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Magnetic Susceptibility is the ratio of magnetization to the applied magnetising field intensity. It is a dimensionless quantity. 

Mathematically, 

χ=M/H

Where,

χ = Magnetic susceptibility

M= Magnetization

H = Field intensity

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Types of Magnetic Materials

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Diamagnetic Material

• Magnetic materials that line up with the magnetic field are known as diamagnetic materials. 
• For diamagnetic materials, the magnetic susceptibility value is χ<0. 
• This relationship indicates that magnetic susceptibility is always negative for diamagnetic materials. 

Diamagnetical Material

• The magnets repel these materials, which cause them to shift from a stronger magnetic field to a lesser magnetic field. 
• These materials are temperature insensitive. 
• Magnetization in diamagnetic materials is in the opposite direction. 
• The diamagnetic materials' magnetization intensity is within a certain range. 
• The relative permeability of any diamagnetic substance is almost the same.

Read More: The Solenoid and the Toroid

Diamagnetic material examples:

1. Gold 
2. Tin 
3. Mercury 
4. Water 
5. Copper 
6. Zinc 
7. Bismuth 
8. Silver 
9. Antimony
10. Marble 
11. Glass 
12. NaCl etc. 

Paramagnetic Materials

• The term paramagnetic refers to magnetic materials that align with the magnetic field. 
• Magnetic susceptibility for paramagnetic materials is >0, implying that it is always a tiny positive number. 
• Different dependencies exist for paramagnetic materials. 
• Temperature is a dependent quantity for each paramagnetic substance. 
• The magnetic field can be reduced by increasing the temperature of paramagnetic materials.
• The relative permeability of these materials ranges between 1.00001 and 1.003. 

Paramagnetic Materials

The following are some examples of paramagnetic materials:

1. Alkaline earth metal
2. Aluminium
3. Oxygen 

Read More: Magnetic Flux

The magnetization of paramagnetic materials can be calculated using Curie's law. As a result, according to Curie's law, the magnetization formula is:

M = χ H = {C / T x H}

Where,

M = magnetization

C = material-specific Curie constant

χ = magnetic susceptibility

H = auxiliary magnetic field

T = absolute (Kelvin) temperature

Ferromagnetic Materials

• Ferromagnetic materials are magnetic materials that are strongly magnetised in a magnetic field. 
• The magnets attract them strongly, and they travel from lesser magnetic fields to stronger magnetic fields. 
• They do not have constant susceptibilities in most cases.
• The magnetization is not proportional to the applied field strength. 
• The positive values of measured ferromagnetic susceptibilities are rather high. 
• The relative permeability value ranges between 1,000 and 100,000. 
• The following are some examples of ferromagnetic materials:

1. Iron 
2. Cobalt 
3. Nickel (and their alloys)

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Things to Remember

• The magnetic susceptibility of a substance can reveal information about its behaviour. 
• Magnetic susceptibility can explain whether or not a substance may be attracted or repelled by a magnetic field.
• It is a dimensionless quantity.
• Mathematically, it can be expressed as- χ=M/H. Where, χ = Magnetic susceptibility, M= Magnetization and H = Field intensity
• When paramagnetic materials come across higher magnetic fields, they can be attracted by the magnetic field. This happens when they align with the applied magnetic field.
• Magnetic field alignment is not possible in diamagnetic materials. As a result, each substance is pushed away from higher magnetic fields and toward lower magnetic fields.
• The material's magnetization is always higher than the applied field. 
• Quantitative measurements can be applied to magnetic susceptibility values. 
• Magnetic susceptibility can provide us with the necessary information depending on the material structure. 
• Magnetic Susceptibility can also reveal information about energy levels and material bonding.

Read More: Magnetism and Gauss’s Law