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Magnetism and Classification of Magnetic Materials

Magnets and magnetic fields produce a classic phenomenon that is known as Magnetism. Its origin is dependent on the orbital movements of the electrons of the element. It might be a surprising fact for you, but every matter has some magnetic property, and the only difference that is there is in respect to the amount of magnetism present. Moreover, the classification of the materials is done based on their magnetic properties.

Types of Magnetic Materials

Now, moving on to the classification of a magnet; it happens based on magnetism and goes as follows:

  1. Diamagnetism

  2. Paramagnetism

  3. Ferromagnetism

  4. Ferrimagnetism

  5. Antiferromagnetism.

The matters showing Paramagnetism and Diamagnetism are the ones that do not exhibit any magnetic interactions. However, the ones in the other three groups show a long-range magnetic order after certain temperature conditions.

Ferromagnetic and Diamagnetic materials are opposite to each other. When the former one shows magnetic behaviour, the latter one does not exhibit any such property.

What is Diamagnetism?

Now, how should we define diamagnetic materials?

A diamagnetic material is one that has a very low or minimal magnetic effect due to the absence of any unpaired electrons in them. 

Another way for explaining diamagnetic meaning is through Lenz’s law. It states that diamagnetic materials get induced dipoles in the presence of an external magnetic field, and this happens in such an order that the magnetic field and the induced dipoles repel each other.

What is Diamagnetic Material?

Moving on to the substances available globally, what are diamagnetic materials?

In 1845, Michael Faraday discovered diamagnets and the meaning of diamagnetic materials. Further, with the creation of the modern-day periodic table, experts commented and proved that most of the elements are Diamagnetic, like Gold, Silver, Copper, etc. These di-magnetic elements cover the majority of the table, and the other categories have a lesser number of elements. Moreover, semiconductors are the best diamagnetic materials. They also exhibit the diamagnetic field and this perfect diamagnetism in the superconductor is known as the Meissner effect.

Diamagnetic Properties

After understanding the diamagnetic definition well, let us move further with the properties. Properties of the diamagnetic materials are:

  1. The diamagnetic materials have all the paired electrons, and none of the electrons is the valance, resulting in the absence of atomic dipoles in these materials. This happens because the overall magnetic moment of each atom in the compound cancels out.

  2. In the presence of the magnetic field, there is a repulsion between the diamagnetic substance and the magnet.

  3. The field weakly repels the substances having diamagnetism; thus in the non-uniform field’s presence, these substances move from the stronger region of the magnetic field to the weaker one.

  4. In comparison to the magnetizing field, magnetization intensity is lower in the negative direction, and proportional.

  5. Diamagnetic materials have lower and negative magnetic susceptibility.

  6. The relative permeability is also a bit lower than unity.

  7. The materials that exhibit diamagnetism do not obey Curie’s Law. They are independent of the action of temperature.

  8. When suspending a rod of some material following diamagnetic definition in the uniform magnetic field, it comes to rest in the perpendicular direction with respect to the magnetic field. This happens as the magnetic field is highest at the poles.

  9. A diamagnetism-exhibiting liquid placed in a U-shaped tube gets depressed in the limb that is in the middle of the magnetic poles.

  10. The dipole moment of the di-magnetic substances is lower and in the opposite direction of the magnetic field H.

  11. When placing a diamagnetic liquid in a watch glass and then keeping the glass between two poles that stays closely, liquid accumulates at the sides of the glass. The liquid exhibits depression in the middle as the magnetic field is the strongest there.

  12. When placing a diamagnetic liquid in a watch glass and then keeping the glass between two poles that stay far apart, liquid accumulates in the middle of the glass. This reaction occurs because the magnetic field is weaker in the centre.

Fun Facts on Diamagnetic Substances:

Diamagnetic properties cause the objects to levitate. Unbelievable, right? But this is a proven fact! 

The reason is that the diamagnetic materials get magnetism only in the presence of the magnetic field, and these induced fields are opposite to the acting magnet. This is why they get utilized in many experiments for levitating the objects.

Moreover, even the Maglev train works with the help of this property of diamagnetism. Additionally, once a frog also got levitated in the presence of a strong magnetic field in an experiment.

FAQ (Frequently Asked Questions)

Q1: What is the Meissner Effect?

Ans: Whenever any substance is under the process of transition for becoming a superconductor, it starts losing the resistance to the electric current when cooled below the transition temperature (the temperature that is highly close to absolute zero). During the process, the substance starts expelling out the magnetic field, and this is known as the Meissner effect. 

The German physicists R. Ochsenfeld and W. Meissner discovered the Meissner effect in 1933 and unveiled that this effect is the common property of every superconductor.

Q2: What are the Superconductors and What is the Magnetic Susceptibility?

A: Superconductors are materials that exhibit diamagnetic properties. They have a volume susceptibility of Xv = -1, i.e. dimensionless. They are the perfect di-magnets and obey complete di-magnetic screening. For example, Aluminium, cuprates, etc.

The magnetic susceptibility of a material is the measurement of how much magnetic can it become after the application of some external magnetic field. In other words, this is the magnetization M’s ratio to H (the external magnetic field that is applied. The susceptibility of superconductors is generally around -1.