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# Diamagnetic Materials - Properties And Applications

Magnetic force is an attractive force between a magnet and a magnetic material. Diamagnetic materials refer to the materials that repel the magnetic field. Materials like water, wood, plastic and other similar materials are non-magnetic and are known as Diamagnetic materials.

• What are Diamagnetic materials?
• Discovery of Diamagnetism
• Properties of Diamagnetic Materials
• Superconductors
• Meissner Effect
• Examples of Diamagnetic Materials
• Application of Diamagnetic Materials
• Importance of Diamagnetic Materials
• Practice Problems

## What are Diamagnetic materials?

Diamagnetic materials are that show repelling properties to the magnetic field. However, the magnetisation is in the opposite direction of the magnetic field. Thus, this magnetism shown by the materials is called diamagnetism.

The electrons in an atom revolve around the nucleus resulting in orbital angular momentum. So the magnetic momentum in an atom of a diamagnetic material is zero. Some examples of diamagnetic materials are copper, wood, plastics, etc.

In diamagnetic materials, an applied magnetic field induces a dipole, and these dipoles oppose the magnetic field. Thus, the materials which have electron pairs have the property of diamagnetic materials. This property is known as diamagnetism.

## Discovery of Diamagnetism

Diamagnetism was discovered by Brugmans in 1778. He discovered that magnetic fields repelled bismuth. In the year 1845, Michael Faraday demonstrated the diamagnetic property when a magnetic field is applied.

## Properties of Diamagnetic Materials

• Diamagnetic materials are perpendicular to the direction of the magnetic field to get suspended.
• They travel from strong to weak areas of the magnetic field when suspended.
• The relative permeability of less than 1.
• Magnets resist diamagnetic materials.
• The susceptibility of diamagnetic materials is negligible, tiny and independent of temperature. Thus Curie’s law does not apply to these materials.
• Magnetic momentum = 0
• Magnetisation strength is low to a negative number and directly proportional to the magnetic field.
• The magnetic dipole moment is low and changed in the opposite direction as the magnetic field.

## Superconductors

Superconductors are strong diamagnetic materials with volume susceptibility of χv = − 1 (dimensionless). They show an ideal diamagnetic screening and are considered perfect diamagnets because they expel all magnetic fields.

## Meissner Effect

When a permanent magnet is brought closer to a superconductor, a current is induced by the superconducting material that completely opposes the magnetic field applied by the permanent magnet. The superconductor drives out the magnetic field that is applied so that the field is zero in its interior. So the superconductor acts as a perfect diamagnet in the Meissner state.

## Examples of Diamagnetic Materials

Common examples of diamagnetic materials are as follows:

• Mercury
• Water
• Diamond
• Graphite
• Bismuth
• Carbon
• Silver
• Neon
• Copper
• Pyrolytic carbon

## Application of Diamagnetic Materials

Diamagnetic materials can be used in various ways. Some of them are listed below:

• Diamagnetic materials have the Bohr magneton = 0
• If the materials have an odd number of electrons, it doesn’t show diamagnetism.
• Superconductors are classified as perfect diamagnetic materials.
• The Meissner effect explains how materials can be levitated in the presence of powerful permanent magnets.

## Importance of Diamagnetic Materials

• Diamagnetic materials are used in Magnetic Resonance Imaging (MRI).
• Pyrolytic graphite is a diamagnetic material that can float in the magnetic field.
• Bismuth is the strongest diamagnetic material used in guns.
• Diamagnetic materials don't melt in heat.

## Practice Problems

Q1. What is the magnetic momentum of a diamagnetic material?

A. Greater than zero
B. Lesser than zero
C. One
D. Zero

In diamagnetic materials, the atoms have no magnetic moment when there is no applied field.

Q2. Diamagnetic materials are independent of _________.

A. Magnetic field
B. Temperature
C. Pressure
D. None of the above

The susceptibility of diamagnetic materials is negligible, tiny and independent of temperature.

Q3. Which of the following is not a diamagnetic material?

A. Water
B. Iron
C. Copper
D. Diamond

Iron is a magnetic material.

Q1. Why is water diamagnetic?
Answer : Water is diamagnetic because it has two bonding electron pairs between a hydrogen and oxygen atom. Thus a magnetic field near water induces its magnetic field that repels the magnet.

Q2. What is Magnetic Susceptibility?