Diamagnetic Materials Theory with Examples

Introduction

You think water, woods, organic compounds, petroleum, plastics, copper, etc., are non-magnetic. But are you sure? These materials are Diamagnetic Materials. A few materials might not have any magnetic moment, but others may have a high magnetic moment interaction. Diamagnetic materials are substances that are not attracted to any magnetic field.

However, if you think that they are not attracted to any magnetic field and are not of that much use, you are mistaken.

Diamagnetic materials are widely used and have many applications. You must have heard about superconductors. Superconductors are also known for their Diamagnetic behaviour. Some examples of superconductors are copper oxide, aluminium, etc. There are many uses of superconductors and Diamagnetic materials in industry and physics.

 What are Diamagnetic Materials?

When you put a Diamagnetic material in a magnetic field, you will notice that it does not interact in the field. This is because these materials are freely magnetised. These materials are known as Diamagnetic Materials. They do not show any interaction in the magnetic field because they do not have any unpaired electrons. All of the electrons are paired, making the magnetic dipole 0.

In the 1700s, the phenomenon of diamagnetism was noticed, but it was not named then. After many years Michael Faraday named this phenomenon and told the world about Diamagnetic Materials.

A magnetic field repels diamagnetic materials because the applied magnetic field induces another magnetic field near the material in the opposite direction, which causes the repulsive force. This way, there is no magnetic moment.

What causes Diamagnetism in Diamagnetic Materials?

The number of electrons can highly be responsible for determining whether the object is Diamagnetic or not. All the electrons of a Diamagnetic Material are coupled. It means no free electrons left to pair. Because of this, there is no total magnetic moment concerning that atom. If any material has all paired electrons, then the material will show Diamagnetic behaviour.

Diamagnetic Materials properties

• They do not have dipoles. The magnetic moment is zero because of paired electrons.
• In a magnetic field, a magnet will repel all Diamagnetic Materials.
• The magnetic susceptibility is negligible.
• The permeability ratios of these materials are less than unity.
• The magnetisation strength (I) of these materials is less than unity.
• Curie’s law does not apply to these materials because the temperature does not affect the magnetisation.
• The dipole moments of Diamagnetic Materials are tiny and are in the opposite direction of the magnetic field.

• If a Diamagnetic liquid is put on the watch glass and placed over two pieces of the pole that are at a distance from each other, then the liquid settles in the middle because it has the weakest magnetic field.

Application of Diamagnetic Materials

Some Diamagnetic Materials can be levitated because they expel the magnetic field within that material. It is possible only if the material is stronger and larger.

In response to superconductors, the Diamagnetic Materials have zero magnetic fields internally.

Diamagnetic Materials and superconductors with high temperatures. They are made from materials that require expensive processing and fluids to reach the state in which they are superconducting. The superconductors, which are blue, are known as the perfect Diamagnets.

 Meissner Effect

Meissner’s effect states that if a permanent magnet is placed close to any superconductor, the superconductor’s material induces a current in the opposite direction of the magnetic field of the permanent magnet. It results in zero magnetic fields in the interior. In this state, perfect diamagnetism behaviour is shown by the superconducting material, a diamagnetic material.

 Important points to remember

Gases, liquids, and solids can all occur in the form of Diamagnetic Material. The property of Diamagnetic Material occurs in all materials independent of temperature. Their effect is so mild compared to paramagnetic and ferromagnetic materials.

Diamagnetic Materials Examples

• Water
• Gold
• Copper
• Bismuth
• Mercury
• Silver
• Lead
• Carbon
• Superconductor
• NaCl

 Conclusion

The property of Diamagnetic Materials is exhibited by every material, which shows a weak contribution of the material in a magnetic field. However, compared to ferromagnetic materials and paramagnetic materials, they are much stronger because of the different forms of magnetism present in those materials. Diamagnetic Materials can also be non-magnetic materials such as water, wood, etc.

Water or water-based Diamagnets have relative permeability less than or equal to 1, making their magnetic susceptibility less than or equal to 0. It means that Diamagnetic Materials show a repelling behaviour towards magnetic fields.

Superconductors are considered the purest form of Diamagnetic Materials. This is because they expel all the magnetic fields. Meissner’s effect or law describes how a superconductor can be a perfect Diamagnetic Material.