type of magnetism (ferromagnetism) in solids such as manganese oxide (MnO) in which adjacent ions that behave as tiny magnets (in this case manganese ions, Mn2+) spontaneously align themselves at relatively low temperatures into opposite, or antiparallel, arrangements throughout the material so that it exhibits almost no gross external magnetism. In antiferromagnetic materials, which include certain metals and alloys in addition to some ionic solids, the magnetism from magnetic atoms or ions oriented in one direction is canceled out by the set of magnetic atoms or ions that are aligned in the reverse direction.

      This spontaneous antiparallel coupling of atomic magnets is disrupted by heating and disappears entirely above a certain temperature, called the Néel temperature, characteristic of each antiferromagnetic material. (The Néel temperature is named for Louis Néel (Néel, Louis-Eugène-Félix), French physicist, who in 1936 gave one of the first explanations of antiferromagnetism.) Some antiferromagnetic materials have Néel temperatures at, or even several hundred degrees above, room temperature, but usually these temperatures are lower. The Néel temperature for manganese oxide, for example, is 122 K (−151° C, or −240° F).

      Antiferromagnetic solids exhibit special behaviour in an applied magnetic field depending upon the temperature. At very low temperatures, the solid exhibits no response to the external field, because the antiparallel ordering of atomic magnets is rigidly maintained. At higher temperatures, some atoms break free of the orderly arrangement and align with the external field. This alignment and the weak magnetism it produces in the solid reach their peak at the Néel temperature. Above this temperature, thermal agitation progressively prevents alignment of the atoms with the magnetic field, so that the weak magnetism produced in the solid by the alignment of its atoms continuously decreases as temperature is increased.

* * *

Universalium. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • Antiferromagnetism — In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usuallyrelated to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. This …   Wikipedia

  • antiferromagnetism — antiferomagnetizmas statusas T sritis chemija apibrėžtis Kristalinės medžiagos magnetinė būsena, kai magnetiniai momentai gardelėse arba domenuose antilygiagretūs. atitikmenys: angl. antiferromagnetism rus. антиферромагнетизм …   Chemijos terminų aiškinamasis žodynas

  • antiferromagnetism — antiferomagnetizmas statusas T sritis fizika atitikmenys: angl. antiferromagnetism vok. Antiferromagnetismus, n rus. антиферромагнетизм, m pranc. antiferromagnétisme, m …   Fizikos terminų žodynas

  • antiferromagnetism — noun see antiferromagnetic …   New Collegiate Dictionary

  • antiferromagnetism — noun a phenomenon, similar to ferromagnetism, in which magnetic domains line up in a regular pattern, but with neighbouring electron spins pointing in opposite directions; materials showing this effect …   Wiktionary

  • antiferromagnetism — Смотри Антиферромагнетизм, АФМ …   Энциклопедический словарь по металлургии

  • antiferromagnetism — a phenomenon where complete magnetic moment cancellation occurs as a result of antiparallel coupling of adjacent atoms or ions; the macroscopic solid possesses no net magnetic moment …   Mechanics glossary

  • antiferromagnetism — an·ti·fer·ro·mag·net·ism …   English syllables

  • antiferromagnetism — noun magnetic field creates parallel but opposing spins; varies with temperature • Derivationally related forms: ↑antiferromagnetic • Hypernyms: ↑magnetism, ↑magnetic attraction, ↑magnetic force • Hyponyms: ↑ferrimagnet …   Useful english dictionary

  • antiferromagnetic — antiferromagnetism /an tee fer oh mag ni tiz euhm, an tuy /, n. /an tee fer oh mag net ik, an tuy /, adj. Physics. noting or pertaining to a substance in which, at sufficiently low temperatures, the magnetic moments of adjacent atoms point in… …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”