Importance of Diamagnetic Force

The generation of the magnetic field in the matter is contributed to the spinning motion of the electrons and the interactions between them. The response of different materials to magnetism forms the basis of the classification of matter into paramagnetic, diamagnetic and ferromagnetic. All materials have some sort of magnetic permeability in them, some have higher and some have lower. Diamagnetic materials are those that are repelled by a magnetic field. This is due to the induction of a magnetic field of their own on the application of an external magnetic field. The induced field is in the opposite direction which causes the repulsive force, called the Diamagnetic force. The materials which possess diamagnetism, have no atomic dipole as they have paired electrons. The discovery of diamagnetism was made by Anton Brugmans on bismuth. Later in 1845, Michael Faraday demonstrated the property of magnetism in the matter and classified them as paramagnetic and diamagnetic. To understand the importance of diamagnetic force, first, understand the properties of diamagnetism.

Properties of diamagnetic force

1. Diamagnetic materials are repulsive to magnetic force.

2. Diamagnetic materials have no atomic dipoles as the resultant magnetic moment of every atom is zero because of the presence of paired electrons.

3. The magnetization intensity (denoted by ‘I’) is either small or negative and proportional to the magnetic field applied.

4. Diamagnetic substances are weakly repelled by the magnetic field so on the application of a non-uniform field externally, these materials move from the stronger part of the field to the weaker part of the field.

5. The relative permeability of diamagnetic materials is less than unity but not significantly.

6. Diamagnetic materials do not obey Curie’s law and are independent of the temperature.

7. When diamagnetic material is kept in a U-tube and one limb is put between the poles of a magnet, the level will depress in that limb.

8. Magnetic susceptibility of a diamagnetic material is negative and small.

9. The dipole moment of the diamagnetic substance is small and opposite in direction to the magnetic field.

10. When suspended in a uniform external magnetic field, the diamagnetic material rotates and comes to rest with the length of material perpendicular to the field direction as the field is strongest at the poles of material.

11. The diamagnetism is produced due to the induced dipole moment as the orbital motion of electrons in atoms changes on the application of an external magnetic field.

12. On keeping the diamagnetic liquid in a watch glass kept on the two poles of a magnet and are close to each other, the liquid tends to move towards the edges of the watch glass which leaves a depression in the centre as the field is strongest at that place.

13. Similarly, On keeping the diamagnetic liquid in a watch glass kept on the two poles of a magnet and are significantly apart from each other, the liquid tends to move towards the centre of the watch glass as the field is weakest at that place.

Importance of diamagnetic force

The uses of Diamagnetic force can be understood by understanding the applications of the force, which are as follows:

1. Levitation

As diamagnetism can be defined as the expulsion of the magnetic field in a material, the materials with strong diamagnetism can be levitated or they can be used to levitate magnets depending on their size and strength. Many experiments have been conducted to use this property for scientific benefit. A thin pyrolytic graphite slice can be floated stably in an external magnetic field as it shows strong diamagnetism. A university in the Netherlands has successfully levitated water and other substances, most specifically a frog. Recently in 2009, NASA announced its successful levitation of mice with a superconducting magnet, this is an important step because humans are more biologically similar to frogs.

2. Imaging

Superconducting magnets are an important component of MRI systems i.e. Magnetic Resonance imaging. MRI systems have been highly useful in the medical field in diagnostics and imaging. Strong magnetic fields are required for the highest quality imaging. The large magnetic field is maintained by superconductors as they provide a good amount of energy. The materials are expensive but they keep the system economical and feasible to use.

3. Other uses

• Superconductors that operate at high temperatures (-100 K) often require special processing and cryogenic fluids to become superconducting.

• Superconductors exhibit no internal magnetic fields as a result of their diamagnetic properties. A powerful permanent magnet can easily levitate certain materials, creating the Meissner effect.

• The interior of a superconductor is free of magnetic fields as a result of its expulsion from a magnetic field applied to it. This is Meissner’s effect. 

• Bismuth, which is a superconductor, is used to make guns. 

Conclusion

Diamagnetic force is an inherent property of some material. They generate a magnetic field when kept in an external field, the direction of which is opposite and the nature of it is repulsive.

The importance of diamagnetic force is not yet known as the knowledge and the technology to understand it is not there yet. The full potential of the force can be unlocked in the future, with the help of proper advancements necessary. For now, the concept of diamagnetism is limited to levitation, cryo fluids and superconductors, and magnetic resonance imaging. All of these are being applied one way or another to conduct successful experiments and tasks like diagnostics in medicine.