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 is, like ferromagnetismand ferrimagnetism, a manifestation of ordered magnetism. Generally, antiferromagnetic order may exist at sufficiently low temperatures, vanishing at and above a certain temperature, the Néel temperature(named after Louis Eugène Félix Néel, who had first identified this type of magnetic ordering [L. Néel, "Propriétées magnétiques des ferrites; Férrimagnétisme et antiferromagnétisme", Annales de Physique (Paris) 3, 137-198 (1948).] ). Above the Néel temperature, the material is typically paramagnetic.
When no external field is applied, the antiferromagnetic structure corresponds to a vanishingtotal magnetization. In a field, a kind of
ferrimagneticbehavior may be displayedin the antiferromagnetic phase, with the absolutevalue of one of the sublattice magnetizations differing from that of theother sublattice, resulting in a nonzero net magnetization.
The magnetic susceptibility of an antiferromagnetic material typically shows a maximum atthe Neel temperature. In contrast, at the transition between the ferromagneticto the paramagnetic phases the susceptibility will diverge. In the antiferromagneticcase, a divergence is observed in the "staggered susceptibility".
Various microscopic (exchange) interactions between the magnetic moments or spinsmay lead to antiferromagnetic structures. In the simplest case, one may consider an
Ising modelonan bipartitelattice, e.g. the simple cubic lattice, with couplings between spins at nearest neighbor sites. Depending onthe sign of that interaction, ferromagnetic or antiferromagneticorder will result. Geometrical frustrationor competing ferro- and antiferromagnetic interactions may lead to differentand, perhaps, more complicated magnetic structures.
Antiferromagnetic materials occur less frequently in nature than ferromagnetic ones. An example is the heavy-fermion superconductor URu2Si2. Better known examples include metals such as
chromium, alloys such as iron manganese (FeMn), and oxides such as nickel oxide (NiO). There are also numerous examples among high nuclearity metal clusters. Organic molecules can also exhibit antiferromagnetic coupling under rare circumstances, as seen in radicals such as 5-dehydro-m-xylylene.
Antiferromagnets can couple to ferromagnets, for instance, through a mechanism known as
exchange bias, in which the ferromagnetic film is either grown upon the antiferromagnet or annealed in an aligning magnetic field, causing the surface atoms of the ferromagnet to align with the surface atoms of the antiferromagnet. This provides the ability to "pin" the orientation of a ferromagnetic film, which provides one of the main uses in so-called spin valves, which are the basis of magnetic sensors including modern hard driveread heads.
Antiferromagnetism plays a crucial role in
giant magnetoresistance, as had been discovered in 1988 by the Nobel prizewinners Albert Fertand Peter Grünberg.
There are also examples of disordered materials (such as iron phosphate glasses) that become antiferromagnetic below their Néel temperature. These disordered networks 'frustrate' the antiparallelism of adjacent spins; i.e. it is not possible to construct a network where each spin is surrounded by opposite neighbour spins. It can only be determined that the average correlation of neighbour spins is antiferromagnetic. This type of magnetism is sometimes called "speromagnetism".
Geometrically frustrated magnet
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antiferromagnetism — ▪ physics 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… … Universalium
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