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# Explain in brief: Diamagnetism

Last updated date: 12th Aug 2024
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Hint: Magnetic substances are divided into three characteristics depending on their properties. They are diamagnetic substances, paramagnetic substances and ferromagnetic substances. Diamagnetism is the property of magnetic substances such as ferromagnetism and paramagnetism. The substances which when placed in an external magnetizing field, get magnetized feebly in a direction opposite to the magnetizing field are called diamagnetic substances.

Diamagnetic substances get magnetized in a direction opposite to the magnetizing field. Examples of a diamagnetic substance are copper, silver, gold, bismuth, zinc, lead, glass, marble, sodium chloride, water and gases such as helium and argon.

Properties: Diamagnetic substances are feebly magnetized and their induced magnetic dipole moment is directed opposite to the magnetizing field $H$. For them, relative permeability is smaller than one. Their magnetic susceptibility is negative and small. $B$ (Magnetic induction field) inside the diamagnetic substances is less than in vacuum. This is because $B = {\mu _0}(1 + {\chi _m})H$.
where, ${\mu _0}$ is the permeability of vacuum or medium and ${\chi _m}$ is the magnetic susceptibility. Magnetic susceptibility is the ratio of intensity of magnetization of a material and the magnetizing field.

Diamagnetic substances move from stronger regions of the magnetizing field to the weaker regions. They are repelled by the bar magnet. If a bar of diamagnetic substance is suspended between the pole pieces of a magnet, it aligns itself perpendicular to the magnetic field of the magnet.

Note:Diamagnetic substances do not obey Curie’s Law. Curie’s Law states that the magnetic susceptibility is inversely proportional to the temperature in Kelvin.Diamagnetic substances do not obey Curie’s Law. The properties possessed by diamagnetic substances are independent of temperature. This is because diamagnetism originates from the magnetic moment associated with the orbital motion of electrons and does not consider the vibrations in a molecule which are the cause of increase or decrease in temperature.