diamagnetism

diamagnetism [dī΄əmag′nə tiz΄əm]

n.

1. the property that certain substances have of being weakly repelled by both poles of a magnet

2. diamagnetic force

3. diamagnetic phenomena

4. the science that deals with such phenomena and substances

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See diamagnetic.

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Kind of magnetism characteristic of materials that line up at right angles to a nonuniform magnetic field and that partly expel from their interior the magnetic field in which they are placed.

In most materials, the magnetic fields of the electrons balance each other and add up to zero. However, when placed in an external magnetic field, the interaction of this field with the electrons induces an internal field in the opposite direction. The substance can then be weakly repelled by magnetic poles. Examples of diamagnetic substances include bismuth, antimony, sodium chloride, gold, and mercury.

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▪ physics

      kind of magnetism characteristic of materials that line up at right angles to a nonuniform magnetic field and that partly expel from their interior the magnetic field in which they are placed. First observed by S.J. Brugmans (1778) in bismuth and antimony, diamagnetism was named and studied by Michael Faraday (Faraday, Michael) (beginning in 1845). He and subsequent experimenters found that some elements and most compounds exhibit this “negative” magnetism. Indeed, all substances are diamagnetic: the strong external magnetic field speeds up or slows down the electrons orbiting in atoms in such a way as to oppose the action of the external field in accordance with Lenz's law.

      The diamagnetism of some materials, however, is masked either by a weak magnetic attraction ( paramagnetism) or a very strong attraction ( ferromagnetism). Diamagnetism is observable in substances with symmetric electronic structure (as ionic crystals and rare gases) and no permanent magnetic (magnetic susceptibility) moment. Diamagnetism is not affected by changes in temperature. For diamagnetic materials the value of the susceptibility (a measure of the relative amount of induced magnetism) is always negative and typically near negative one-millionth.

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