diamagnetism (rus. диамагнетизм) — (from Greek dia meaning “divergence“) the property of a substance to become magnetzed in the direction opposite to the external magnetic field.

Description

The external magnetic field induces ring currents in a substance; these currents create orbital magnetic moments directed, according to the Lenz law, towards the external magnetic field. In the absence of an external magnetic field diamagnetics are nonmagnetic, i.e. the magnetic moments are mutually compensated. The creation of the diamagnetic moment involves all electrons of the atoms, as well as free charge carriers in metals and semiconductors.

Diamagnetism is inherent in many substances, but in most cases the contribution of the diamagnetic response is relatively small as compared to the paramagnetic and ferromagnetic responses and represents only a small portion of the total magnetisation of the substance. Diamagnetics include: inert gases; Cu; Ag; Au; Zn; Cd; Ge; Si; Sb; P and other simple substances; many inorganic compounds, such as H2O, MgO, NaCl, ZnSO4, saturated hydrocarbons, fatty acids, cyclic and other organic compounds.

Diamagnetism is also inherent in the superconducting state of a substance, i.e. all superconducting substances at a temperature and external magnetic field below critical values are ideal diamagnetics with the largest absolute values of diamagnetic susceptibility . Diamagnetism of superconductors has a very special nature: in contrast to the diamagnetism of the substances listed above, it is not due to intra-atomic properties (currents), but is caused by macroscopic undamped currents at the surface of the superconductor (Meissner effect), whose strength and configuration automatically completely compensate the external magnetic field in the whole volume of the superconductor.

Authors

  • Streletskiy Alexey V.
  • Soldatov Eugene S.

Sources

  1. Diamagnetism // Physical encyclopedia Ed. by A.M. Prokhorov (in Russian). V. 1. — Moscow.: The Great Soviet Encyclopedia, 1992. 612–614 pp.
  2. Diamagnetics // Chemical Encyclopedic Dictionary Ed. by I. L. Knunjanc (in Russian). — Moscow: Sovetskaja ehnciklopedija, 1983. 158 p.

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