Ferromagnetism

Definition: Ferromagnetism

Ferromagnetism

Noun

1. Phenomenon exhibited by materials like iron (nickel or cobalt) that become magnetized in a magnetic field and retain their magnetism when the field is removed.

Specialty Definitions: Ferromagnetism

Domain	Definitions
Mining	A. Spontaneous magnetic orientation of all magnetic moments in the same direction. The orientation can be reversed by an external magnetic field b. Strong magnetic susceptibility caused by overlap of adjacent d orbitals; e.g., iron, nickel, cobalt, and numerous alloys, both ferrousand nonferrous. CF:antiferromagnetism; ferrimagnetism. e.g., iron, nickel, cobalt, and numerous alloys, both ferrousand nonferrous. CF:antiferromagnetism; ferrimagnetism. (references)
Physics	A phenomenon by which the magnetic moments of neighbouring atoms are aligned approximately in the same direction due to mutual interaction. Source: European Union. (references)
Source: compiled by the editor from various references; see credits.

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Specialty Definition: Ferromagnetism

(From Wikipedia, the free Encyclopedia)

Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. It is responsible for most of the magnetic behavior encountered in everyday life, and is the basis for all permanent magnets (as well as the metals that are attracted to them). Some examples of ferromagnetic materials are iron, cobalt, nickel, and gadolinium.

Physical origin

The property of ferromagnetism is due to the direct influence of two effects from quantum mechanics: spin and the Pauli exclusion principle.

The spin of an electron has a magnetic dipole moment and creates a magnetic field. (The classical analogue of quantum-mechanical spin is a spinning ball of charge, but the quantum version has distinct differences, such as the fact that it has discrete up/down states that are not described by a vector.) In many materials (specifically those with a filled electron shell), however, the electrons come in pairs of opposite spin, which cancel one another's dipole moments. Only atoms with unpaired electrons (partially filled shells) can experience a net magnetic moment from spin. A ferromagnetic material has many such electrons, and if they are aligned they create a measurable macroscopic field.

The spins/dipoles tend to align in parallel to an external magnetic field, an effect called paramagnetism. (A similar effect due to the orbital motion of the electrons, which effectively forms a microscopic current loop that also has a magnetic dipole moment, is called diamagnetism.) Ferromagnetism involves an additional phenomenon, however: the spins tend to align spontaneously, without any applied field. This is a purely quantum-mechanical effect.

According to classical electromagnetism, two nearby magnetic dipoles will tend to align in opposite directions (which would create an antiferromagnetic material). In a ferromagnet, however, they tend to align in the same direction because of the Pauli principle: two electrons with the same spin cannot lie at the same position, and thus feel an effective additional repulsion that lowers their electrostatic energy. This difference in energy is called the exchange energy and induces nearby electrons to align.

At long distances (after many thousands of ions), the exchange energy advantage is overtaken by the classical tendency of dipoles to anti-align. This is why, in an equilibriated (non-magnetized) ferromagnetic material, the spins in the whole material are not aligned. Rather, they organize into domains that are aligned (magnetized) at short range, but at long range adjacent domains are anti-aligned. The transition between two domains, where the magnetization flips, is called a Bloch wall, and is a gradual transition on the atomic scale (covering a distance of about 300 ions for iron).

Thus, an ordinary piece of iron generally has little or no net magnetic moment. However, if it is placed in a strong enough external magnetic field, the domains will re-orient in parallel with that field, and will remain re-oriented when the field is turned off, thus creating a "permanent" magnet. This magnetization as a function of the external field is described by a hysteresis curve. Although this state of aligned domains is not a minimal-energy configuration, it is extremely stable and has been observed to persist for millions of years in seafloor magnetite aligned by the Earth's magnetic field (whose poles can thereby be seen to flip at long intervals). The net magnetization can be destroyed by heating and then cooling (annealing) the material without an external field, however.

As the temperature increases, thermal oscillation, or entropy, competes with the ferromagnetic tendency for spins to align. When the temperature rises beyond a certain point, called the Curie temperature, there is a second-order phase transition and the system can no longer maintain a spontaneous magnetization, although it still responds paramagnetically to an external field. Below that temperature, there is a spontaneous symmetry breaking and random domains form (in the absence of an external field). The Curie temperature itself is a critical point, where the magnetic susceptibility is theoretically infinite and, although there is no net magnetization, domain-like spin correlations fluctuate at all lengthscales.

The study of ferromagnetic phase transitions, especially via the simplified Ising spin model, had an important impact on the development of statistical physics. There, it was first clearly shown that mean-field theory approaches failed to predict the correct behavior at the critical point (which was found to fall under a universality class that includes many other systems, such as liquid-gas transitions), and had to be replaced by renormalization group theory.

References

Charles Kittel, Introduction to Solid State Physics (Wiley: New York, 1996).
John David Jackson, Classical Electrodynamics (Wiley: New York, 1999).

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Ferromagnetism."

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Crosswords: Ferromagnetism

English words defined with "ferromagnetism": Curie point, Curie temperature ♦ ferromagnetic. (references)

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Commercial Usage: Ferromagnetism

Domain	Title
Books	Ferromagnetism (reference) Fundamentals of Solid-State Phase Transitions, Ferromagnetism and Ferroelectricity (reference) Introduction to Applied Solid State Physics: Topics in the Applications of Semiconductors, Superconductors, Ferromagnetism, and the Nonlinear Optica (reference) Introduction to the Theory of Ferromagnetism (The International Series of Monographs on Physics) (reference) Physics of Ferromagnetism (International Series of Monographs on Physics, No 94) (reference) (more book examples)
Source: compiled by the editor from various references; see credits.

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Usage Frequency: Ferromagnetism

"Ferromagnetism" is generally used as a noun (singular) -- approximately 100.00% of the time. "Ferromagnetism" is used about 2 times out of a sample of 100 million words spoken or written in English. Its rank is based on over 700,000 words used in the English language. Some parts-of-speech are not covered due to the samples used by the British National Corpus. (note: percents less than one-hundredth of one percent have been omitted)

Parts of Speech	Percent	Usage per 100 Million Words	Rank in English
Noun (singular)	100%	2	245,945

Source: compiled by the editor from several corpora; see credits.

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Frequency of Internet Keywords: Ferromagnetism

The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com.

Expression	Frequency per Day
ferromagnetism	4
Source: compiled by the editor from various references; see credits.

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Modern Translations: Ferromagnetism

Language		Translations for "ferromagnetism"; alternative meanings/domain in parentheses.
Chinese		�"�磁性. (various references)

Danish		ferromagnetisme. (various references)

Dutch		ferromagnetisme. (various references)

Finnish		ferromagnetismi. (various references)

French		ferromagnétisme. (various references)

German		Ferromagnetismus. (various references)

Greek		σιδηρομαγνητισμός (ferrimagnetism). (various references)

Hungarian		ferromágnesség. (various references)

Italian		ferromagnetismo. (various references)

Korean		강자성. (various references)

Pig Latin		erromagnetismfay

Portuguese		ferromagnetismo. (various references)

Romanian		feromagnetism. (various references)

Spanish		ferromagnetismo. (various references)

Swedish		ferromagnetism. (various references)
Source: compiled by the editor from various translation references.

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Derivations & Misspellings: Ferromagnetism

Derivations
	Words beginning with "ferromagnetism": ferromagnetisms. (additional references)
	Words ending with "ferromagnetism": antiferromagnetism. (additional references)
	Words containing "ferromagnetism": antiferromagnetisms. (additional references)
Misspellings
	"Ferromagnetism" is suggested in spellcheckers for the following: ferromagnet, ferromagnets. (additional references)
Source: compiled by the editor, based on several corpora (additional references).

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Rhyming with "Ferromagnetism"

# of Phoneme Matches	Pronunciation	Word(s) rhyming with "ferromagnetism" (pronounced fe'rōma"gnuti'zum)
12	-r ō m a" g n u t i' z u m	electromagnetism.
10	-m a" g n u t i' z u m	diamagnetism, magnetism.
7	-n u t i' z u m	hypnotism.
6	-u t i' z u m	astigmatism, conservatism, corporatism, despotism, dogmatism, egotism, ergotism, favoritism, helotism, nepotism, patriotism, pragmatism, rheumatism, separatism.
5	-t i' z u m	absolutism, autism, baptism, defeatism, elitism, Irredentism, leftism, pietism, statism, vigilantism.
4	-i' z u m	abolitionism, absenteeism, activism, adventurism, agrarianism, alcoholism, altruism, amateurism, anachronism, aneurism, animism, antagonism, aphorism, atavism, atheism, authoritarianism, barbarism, bilingualism, bolshevism, boosterism, botulism, cannibalism, capitalism, catechism, centralism, chauvinism, classicism, collectivism, colonialism, commercialism, communism, consumerism, counterterrorism, creationism, criticism, cronyism, cubism, cynicism, dandyism, deism, determinism, diastrophism, dimorphism, Druidism, dualism, dwarfism, dynamism, egalitarianism, egoism, embolism, emotionalism, empiricism, entrepreneurialism, environmentalism, eroticism, escapism, ethnocentrism, euphemism, evangelism, expansionism, expressionism, extremism, factionalism, fanaticism, fascism, fatalism, federalism, feminism, fetishism, feudalism, formalism, fundamentalism, futurism, geotropism, gnosticism, gradualism, hedonism, heroism, hooliganism, humanism, idealism, illusionism, imperialism, impressionism, incrementalism, individualism, intellectualism, internationalism, interventionism, isolationism, isomorphism, jingoism, journalism, legalism, lesbianism, liberalism, lyricism, mannerism, masochism, materialism, mechanism, mercantilism, mesmerism, metabolism, methodism, microorganism, militarism, minimalism, modernism, monasticism, monetarism, monism, monotheism, moralism, multiculturalism, multilateralism, mutualism, mysticism, narcissism, nationalism, nativism, naturalism, negativism, neutralism, nihilism, obstructionism, opportunism, optimism, organism, ostracism, overoptimism, pacifism, paganism, parallelism, parkinsonism, parochialism, pastoralism, paternalism, perfectionism, pessimism, pharisaism, plagiarism, pluralism, polymorphism, polytheism, populism, positivism, professionalism, protectionism, provincialism, puritanism, racialism, racism, radicalism, realism, recidivism, relativism, republicanism, revisionism, romanticism, sadism, satanism, sectarianism, secularism, sensationalism, sexism, skepticism, socialism, stoicism, supernaturalism, surrealism, symbolism, synergism, territorialism, terrorism, theism, tokenism, totalitarianism, tourism, truism, unionism, vandalism, vegetarianism, voluntarism, volunteerism, voyeurism.
3	-z u m	bosom, careerism, chasm, cytoplasm, enthusiasm, iconoclasm, ism, microcosm, neoplasm, orgasm, phantasm, prism, sarcasm, schism, spasm.
Source: compiled by the editor (additional references); see credits.

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Anagrams: Ferromagnetism

Scrabble® Enable2K-Verified Anagrams
	Words within the letters "a-e-e-f-g-i-m-m-n-o-r-r-s-t"
	-2 letters: ferrimagnets, ferromagnets.
	-3 letters: ergotamines, ferrimagnet, ferromagnet, freemartins, manometries, reforesting, remastering.
	-4 letters: antimerger, antireform, ergotamine, fermentors, ferretings, firmaments, forearming, foreigners, freemartin, fromenties, gemmations, generators, germinates, ironmaster, manifester, manometers, merriments, monetarism, morganites, orangeries, rainforest, reformates, ringmaster, stammering, steamering, stereogram.
	-5 letters: agentries, ammonites, antimeres, armigeros, arresting, emigrants, emigrates, engrammes, erigerons, estranger, farseeing, fermentor, ferreting, ferriages, festering, figeaters.
	Words containing the letters "a-e-e-f-g-i-m-m-n-o-r-r-s-t"
	+1 letter: ferromagnetisms.
	+4 letters: antiferromagnetism.
	+5 letters: antiferromagnetisms.
Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro.