Magnetism is a wide-known and widely applied concept that can be explained with the help of the circular motion of electrons. The electrons moving around in a circular orbit inside an atom exhibit the same properties as circular coil-carrying current. This circular motion of the electron in the orbit gives rise to the orbital magnetic moment. Electrons also have the tendency of spinning around their own axis; this gives rise to spin magnetic moments. The magnetic moment of an atom is simply the vector sum of orbital and spin magnetic moments. The magnetism of varying degrees can be seen in para, dia, and ferromagnetic materials.
Magnetic substances are classified as paramagnetic, diamagnetic, and ferromagnetic based on their magnetic properties and their levels of magnetic susceptibility. Diamagnetism is seen in materials with small and negative magnetic susceptibility, paramagnetic materials have small and positive magnetic susceptibility, and ferromagnetic materials have large and positive susceptibility. Let’s study para dia and ferromagnetic materials in detail.
The property of a substance that exhibits a weak magnetic force opposite the applied field’s direction when kept in an external magnetic field is known as Diamagnetism. Diamagnetic substances can only be weakly magnetised. When diamagnetic material is kept in a magnetic field, its flux density is slightly less than flex density in free air. Thus, it can be said that the relative permeability is slightly less than 1 in diamagnetic substances. The magnetic moment of materials that exhibit diamagnetism is zero. Common diamagnetic materials are copper, gold, antimony, bismuth silver, lead, silicon, mercury, etc.
Paramagnetic substances get weakly magnetised in the same direction as the applied field when kept in an external magnetic field. Their unique properties make paramagnetic substances different from ferromagnetic and diamagnetic substances. They have a tendency to move from the weaker to the stronger magnetic field. Furthermore, with a magnetising field, the magnetic flux density in a paramagnetic substance is slightly higher than in empty space. As a result, the relative paramagnetic permeability is somewhat higher than 1.
Each atom in a paramagnetic substance has a permanent magnetic dipole moment that is orientated given the way the atoms spin. When there is thermal motion, however, the direction of magnetic moments might have unpredictable orientations. As a result, this substance’s net magnetic moment is zero. Examples of paramagnetic substances include calcium, lithium, tungsten, aluminium, platinum, etc.
Ferromagnetic substances get strongly magnetised in an external magnetic field in a direction that is the same as the direction of the externally applied field. Even after the magnetic field is removed, these substances retain their magnetic moment. Ferromagnetic materials gravitate from weaker to stronger regions of the external field. Iron, cobalt, and nickel are examples of ferromagnetic materials. Ferromagnetic substances have relative permeabilities in the hundreds of thousands. Similarly, ferromagnetic susceptibilities have huge positive values.
Magnetic moments play a significant role in the spin of ferromagnetic materials. These compounds are made up of a huge number of tiny units called domains. When a ferromagnetic substance is exposed to an external magnetic field, torque occurs in these domains. As a result, the domains rotate and remain parallel to the field’s direction.
In today’s electrical technology, magnets are critical. Magnetism is a science that has been known for thousands of years and is now linked to the modern science of electricity. Magnets are beneficial but also perplexing, as we still can’t fully comprehend or explain certain properties of magnets. Categorising magnetic materials as para, dia, and ferro helps us get better clarity about the world of magnetism and its properties.
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