Magnetic Properties of Materials: Magnetic Materials and Properties

Magnetism and Matter are considered to be one of the most significant concepts in the syllabus of physics which is based on a lot of imagination. Magnetism is not totally connected to the uses of magnets but to the principle and the concepts that are used in various applications. A magnet is an object which produces a magnetic field which, being invisible it is the most notable property of a magnet. 

Magnets and Magnetic Materials

Key terms: Magnetic materials, Magnetization, Ferromagnetic, External magnetic field, Retentivity, Electrons, Magnets

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What is Magnetic Material?

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Magnetic material is one that can repel or attract other materials. The process of attraction or repulsion of these materials depends on the arrangement of electrons, which is known as the magnetic moment of that material. On the basis of the behavior of materials when they are present in a magnetic field, the materials are divided into three categories. The three categories of materials are as follows: 

• Diamagnetic - With regard to the susceptibility χ, a material is diamagnetic if χ is negative. These materials produce negative magnetization when they are placed in the magnetic field. When placed in a magnetic field, these diamagnetic materials are barely magnetized. Diamagnetic substances are the ones that are repelled by magnets. Examples of some diamagnetic materials are silicon, lead, copper, bismuth, etc. They tend to move from the stronger parts of the external magnetic field to the weaker ones. The magnetic dipoles of these substances align in opposition to the applied field, producing an internal magnetic field that opposes the applied field thus producing repulsion. 

• Paramagnetic - In the presence of an external magnetic field, the substances that get weakly magnetized are known as paramagnetic substances. The magnetic dipoles align along the direction of the applied field, reinforcing and enhancing the magnetic field. These substances get weakly attracted to a magnet as they tend to move from a weaker magnetic field to a stronger one. The atoms present in paramagnetic materials have a permanent magnetic dipole moment. When placed in an external field, the field is enhanced and the field lines get concentrated inside the substance. In a non-uniform magnetic field, the material tends to move from a weaker field to a stronger one. Examples of some paramagnetic materials are calcium, aluminum, sodium, etc. The magnetization (M) of paramagnetic materials, discovered by Madam Curie, depends on the temperature (T) and the external magnetic field B.

 M = C x (B/T) 

Where M = Magnetization

C = Curie Constant

B = External magnetic field

T = Temperature

• Ferromagnetic- The materials strongly attracted by the magnetic field are known as ferromagnetic materials. Even when the external field is removed, these materials retain the magnetism. These materials possess the strongest magnetic behavior and thus tend to move from a field of a weak magnetic field to the strongest one. As in a paramagnetic material, the atoms of the ferromagnetic material also possess a dipole moment. But in the case of ferromagnetic materials, the atoms interact with each other to align themselves in a common direction. The arrangement of dipoles in a perfect domain produces strong magnetic fields. In the absence of an electric field, these domains are arranged in a random manner thus canceling the magnetic field of each domain so that the material or substance does not show any magnetic behavior. When an external magnetic field is applied, however, the domains of the material reorient themselves in order to strengthen the external field to produce an internal strong magnetic field along the direction of the external field. Examples of some paramagnetic materials are Iron, nickel, cobalt, etc.

The video below explains this:

Magnetic Properties of Substances value Detailed Video Explanation:

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Magnetic Properties of Materials

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Property 1: Intensity of magnetization (I)

Magnetization or intensity of magnetization indicates the net dipole moment per unit volume.

Property 2: Magnetic intensity or Magnetic field (H)

The external magnetic field that is only produced by electric current flowing in a solenoid is known as magnetic intensity.

Property 3: Magnetic susceptibility

For a small magnetizing field, the intensity of magnetization which material possesses is in direct proportion to the magnetic field (H).

I ∝ H

I = χmH , 

Where χm is the susceptibility of the material.

Property 4: Retentivity

Retentivity is the ability of a material to retain magnetization.

Property 5: Coercivity

The ability of a material to withstand the external magnetic field without being demagnetized. 

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