Diamagnetism

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Diamagnetism is the property of materials that are repelled by a <a href="/facts/Magnetic_field/Ta8Ev588">magnetic field</a>; an applied magnetic field creates an <a href="/facts/Induced_magnetic_field/zxrtXzTN">induced magnetic field</a> in them in the opposite direction, causing a repulsive force. In contrast, <a href="/facts/Paramagnetic/vj1SMbbp">paramagnetic</a> and <a href="/facts/Ferromagnetic/fH3HFnSl">ferromagnetic</a> materials are attracted by a magnetic field. Diamagnetism is a <a href="/facts/Quantum_mechanical/BRc3Mzgr">quantum mechanical</a> effect that occurs in all materials; when it is the only contribution to the magnetism, the material is called diamagnetic. In paramagnetic and ferromagnetic substances, the weak diamagnetic force is overcome by the attractive force of <a href="/facts/Magnetic_dipole/Ny0TVUSX">magnetic dipoles</a> in the material. The <a href="/facts/Permeability_(electromagnetism)/GA7CcRLU">magnetic permeability</a> of diamagnetic materials is less than the <a href="/facts/Vacuum_permeability/nKxRk6J1">permeability of vacuum</a>, μ0. In most materials, diamagnetism is a weak effect which can be detected only by sensitive laboratory instruments, but a <a href="/facts/Superconductivity/pqQAlSzJ">superconductor</a> acts as a strong diamagnet because it entirely expels any magnetic field from its interior (the <a href="/facts/Meissner_effect/VJLdDzzE">Meissner effect</a>).
Diamagnetism was first discovered when <a href="/facts/Anton_Brugmans/fPLkyFDy">Anton Brugmans</a> observed in 1778 that <a href="/facts/Bismuth/75FLjkoX">bismuth</a> was repelled by magnetic fields. In 1845, <a href="/facts/Michael_Faraday/NDcc3lyt">Michael Faraday</a> demonstrated that it was a property of matter and concluded that every material responded (in either a diamagnetic or paramagnetic way) to an applied magnetic field. On a suggestion by <a href="/facts/William_Whewell/t2urFwd2">William Whewell</a>, Faraday first referred to the phenomenon as diamagnetic (the prefix dia- meaning through or across), then later changed it to diamagnetism.
A simple <a href="/facts/Rule_of_thumb/RopfGsJ0">rule of thumb</a> is used in chemistry to determine whether a particle (atom, ion, or molecule) is paramagnetic or diamagnetic: If all electrons in the particle are paired, then the substance made of this particle is diamagnetic; If it has unpaired electrons, then the substance is paramagnetic.

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Diamagnetism