Diamagnetism

Pyrolytic carbon has one of the largest diamagnetic constants[clarification needed] of any room temperature material. Here a pyrolytic carbon sheet is levitated by its repulsion from the strong magnetic field of neodymium magnets

Diamagnetism is the property of materials that are repelled by a magnetic field; an applied magnetic field creates an induced magnetic field in them in the opposite direction, causing a repulsive force. In contrast, paramagnetic and ferromagnetic materials are attracted by a magnetic field. Diamagnetism is a quantum mechanical 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 magnetic dipoles in the material. The magnetic permeability of diamagnetic materials is less than the permeability of vacuum, μ0. In most materials, diamagnetism is a weak effect which can be detected only by sensitive laboratory instruments, but a superconductor acts as a strong diamagnet because it entirely expels any magnetic field from its interior (the Meissner effect).

Diamagnetism was first discovered when Anton Brugmans observed in 1778 that bismuth was repelled by magnetic fields.[1] In 1845, Michael Faraday 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 William Whewell, Faraday first referred to the phenomenon as diamagnetic (the prefix dia- meaning through or across), then later changed it to diamagnetism.[2][3]

A simple rule of thumb is used in chemistry to determine whether a particle (atom, ion, or molecule) is paramagnetic or diamagnetic:[4] 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.

  1. ^ Küstler, Gerald (2007). "Diamagnetic Levitation – Historical Milestones". Rev. Roum. Sci. Techn. Électrotechn. Et Énerg. 52, 3: 265–282.
  2. ^ Jackson, Roland (21 July 2014). "John Tyndall and the Early History of Diamagnetism". Annals of Science. 72 (4): 435–489. doi:10.1080/00033790.2014.929743. PMC 4524391. PMID 26221835.
  3. ^ "diamagnetic, adj. and n". OED Online. Oxford University Press. June 2017.
  4. ^ "Magnetic Properties". Chemistry LibreTexts. 2 October 2013. Archived from the original on 17 March 2020. Retrieved 21 January 2020.