Diamagnetism: Definition, Characteristics and Real-Life Applications

Diamagnetism is an important concept in magnetism that helps us understand how some materials behave when they are placed near magnets. You may have noticed that while some objects stick strongly to magnets, others are pushed away. This happens because of different magnetic properties. This article explains the meaning, causes, examples, what are diamagnetic substances and uses of this interesting magnetic property.

Table of Contents

• What is Diamagnetic and Diamagnetic Substances?
• Why Diamagnetism Occurs?
• Important Properties of Diamagnetic Materials
• Examples and Uses of Diamagnetism in Real Life

What is diamagnetic and Diamagnetic Substances?

Diamagnetism is the property of certain materials in which they are weakly repelled by a magnetic field. So, in simple words, hewn a magnet is brought near a diamagnetic substance, the material moves slightly away instead of getting attracted.

Now you may ask, what is diamagnetic behaviour exactly?

The fact is that diamagnetic materials do not have permanent magnetic moments. When an external magnetic field is applied, they create a very weak magnetic field in the opposite direction. Because of this, they experience repulsion.

Interestingly! This effect is present in all materials, but in most substances, it is very weak and hidden by stronger magnetic effects. Moving ahead, let’s understand what diamagnetic substances are.

“Diamagnetic substances are materials that do not get attracted to magnets and instead show slight repulsion when placed in a magnetic field.”

Their atoms have paired electrons, which means their magnetic effects cancel out.

And you might wonder, why do paired electrons matter? Electrons behave like tiny magnets because of their motion and spin. When electrons are paired, their magnetic effects balance each other. So, the material does not show strong magnetism.

So it can be concluded that diamagnetic substances are materials that show very weak and temporary magnetic behaviour opposite to the applied magnetic field.

Why Diamagnetism Occurs?

Diamagnetism occurs because of small changes in the motion of electrons when a magnetic field is applied to a material. Normally, electrons move around the nucleus in fixed paths. These moving electrons already create tiny magnetic effects inside the atom.

Now, when an external magnetic field is introduced, the paths of these electrons change slightly. This change creates a new magnetic field inside the material that acts in the opposite direction to the applied magnetic field. As a result, the material experiences a very weak repulsive force. This is why diamagnetic substances are gently pushed away from a magnet instead of being attracted to it.

Have you ever noticed that water droplets do not stick to magnets? This happens because water is a diamagnetic material, and it shows a weak repulsion in the presence of a magnetic field.

Important Properties of Diamagnetic Materials

Let’s first understand the most important properties of diamagnetic materials in a simple and clear way. These features help us recognise how a diamagnetic substance behaves in a magnetic field.

1. No Permanent Magnetic Dipoles: Diamagnetic materials do not have permanent magnetic dipoles. This is because their electrons are paired, and their magnetic effects cancel each other. So, the overall magnetic moment of each atom becomes zero.

2. Weak Repulsion from Magnets: One key property is that diamagnetic materials are repelled by magnets. However, the repulsion is very weak and can usually be noticed only in strong magnetic fields.

3. Movement from Strong to Weak Magnetic Field: Diamagnetic substances tend to move from a region of a strong magnetic field to a region of a weak magnetic field. This happens because they always oppose the applied field.

4. Very Small and Negative Magnetisation: Moving ahead, the intensity of magnetisation in diamagnetic materials is very small. The fact is that it is also negative, meaning it acts in the opposite direction of the magnetising field.

5. Negative Magnetic Susceptibility: Magnetic susceptibility tells us how strongly a material responds to magnetism. In diamagnetic materials, this value is small and negative, which shows that they weakly oppose magnetic fields.

6. Relative Permeability Less Than One: The relative permeability of diamagnetic materials is slightly less than one. This means the magnetic field inside the material becomes slightly weaker than the external field.

7. Independent of Temperature: Unlike some magnetic materials, diamagnetic behaviour does not change much with temperature. These materials do not follow Curie’s Law.

8.  Perpendicular Alignment in a Magnetic Field:

When a rod made of diamagnetic material is suspended freely in a uniform magnetic field, it comes to rest in a direction perpendicular to the field.

9. Opposite Magnetic Dipole Moment: The magnetic dipole moment produced in diamagnetic materials is very small and always opposite to the applied magnetic field. This is the main reason for their repulsive behaviour.

10. Origin Due to Change in Electron Motion: Finally, diamagnetism originates because the motion of electrons changes slightly when a magnetic field is applied. This change produces an induced magnetic field in the opposite direction.

Examples and Uses of Diamagnetic Materials in Real Life

First, let’s now look at some common examples of diamagnetic materials found around us, such as Bismuth, Copper, Silver, Gold, Water, Wood, Plastic and Mercury. Now, how does all this come together? Let’s find out.

These materials do not get attracted to magnets. If placed in a strong magnetic field, they move slightly away from the magnet.

Interestingly! Bismuth shows one of the strongest diamagnetic effects among all elements.

Here, one interesting question arises:s: Does diamagnetism have any practical use? Yes! Even though the effect is weak, it is used in several interesting ways.

1. Diamagnetism helps in Magnetic Levitation experiments, where objects float in strong magnetic fields. Scientists have even made small animals like frogs float using powerful magnets!
2. In magnetic shielding, diamagnetic materials are used to reduce unwanted magnetic fields in sensitive scientific instruments.
3. In Medical Technology, MRI machines, understanding magnetic properties like diamagnetism helps improve imaging techniques.
4. For Material Testing, scientists use diamagnetic behaviour to study atomic structure and electron arrangement in materials.

In this article, we understood that Diamagnetism is a magnetic property in which materials show weak repulsion when placed in a magnetic field. This happens because of paired electrons and induced magnetic fields in the opposite direction.