Diamagnetism

The spin motion of electrons and their interaction with one another is what is responsible for the origin of magnetism. The best way to introduce different types of magnetic materials is by describing how materials respond to magnetism. It may come as a surprise to you, but all matter is magnetic. The only difference is that some materials are more magnetic than others. The level of interactions between the magnetic moments is what distinguishes them. In a few materials, there is no collective interaction of atomic magnetic moment while other materials exhibit strong atomic magnetic moment interaction.

Classification of Magnetic Materials

Magnetic properties of a substance are its response to an external magnetic force. Depending on the magnetic properties of solids, they can be classified into three types :

  • Diamagnetic
  • Paramagnetic
  • Ferromagnetic

Given below in the table is the definition of the different types of magnetic materials along with their examples:

Magnetic Material

Definition

Examples

Diamagnetic

Materials that are not attracted to magnetic fields

Mercury, water, copper, bismuth and gold

Paramagnetic

Materials that are weakly attracted to magnetic materials

Magnesium, lithium, molybdenum

Ferromagnetic

Materials that are strongly attracted to magnetic materials

Iron, cobalt and nickel

In the next section, let us look more closely into what diamagnetism is and the various properties of diamagnetic materials.

What is Diamagnetism?

Diamagnetic materials usually repel from a magnet. Technically, these solids create an induced magnetic field in a direction opposite to an externally applied magnetic force and are repelled by the applied magnetic field. This phenomenon is just the opposite behaviour exhibited by paramagnetic materials.

The orbital motion of electrons present on the atoms of diamagnetic solids produces magnetic fields as it creates tiny atomic current loops. When an external magnetic force is applied to a material, these current loops tend to align in such a way as to oppose the applied field.

In diamagnetic materials, there is no permanent net magnetic moment per atom as all the electron are paired. Due to the influence of an external magnetic force, diamagnetic properties arise from the realignment of the electron paths. Most elements in the periodic table like copper, silver, and gold, are diamagnetic in nature. Sebald Justinus Brugmans discovered diamagnets in the year 1778. Michael Faraday further demonstrated that diamagnetism or magnetism is a property of a matter and every material or solid reacts accordingly.

Magnetic Susceptibilities of Diamagnetic Materials at 20°C

Km is the relative permeability which is nothing but a quantity which measures the ratio of the internal magnetization to the applied magnetic field.

Material χm=Km-1

(x 10-5)

Carbon (graphite) -1.6
Ammonia -.26
Silver -2.6
Bismuth -16.6
Carbon (diamond) -2.1
Mercury -2.9
Lead -1.8
Water -0.91
Copper -1.0
Sodium chloride -1.4

The gases N2 and H2 are weakly diamagnetic with susceptibilities -0.0005 x 10-5 for N2 and -0.00021 x 10-5 for H2. The gases N2 and H2 are weakly diamagnetic with susceptibilities -0.0005 x 10-5 for N2 and -0.00021 x 10-5 for H2.

Stat tuned with BYJU’S to learn more about magnetism and diamagnetism with the help of interactive video lessons.


Practise This Question

An inflated balloon is rubbed with a woollen cloth and in another case, a ballpen refill is rubbed with polythene. When they are brought closer, it is observed that they attract each other. What can we understand by this?