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Topic: Ferromagnetic interaction

Related Topics

Antiferromagnetic interaction

Ferromagnetism

Mean Field Theory

Ferrimagnetism

Curie temperature

Magnetism

Phase transition

Ising model

Ferrite

Solenoid

Ozone

Ultraviolet light

Chlorine

Nickel

Cryptosporidium

	Encyclopedia :: encyclopedia : Ferromagnetism (Site not responding. Last check: 2007-11-02)
		Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism.
		Ferromagnetic metal alloys whose constituents are not themselves ferromagnetic in their pure forms are called Heusler alloys, named after Fritz Heusler (1903).
		In 2004, it was reported that a certain allotrope of carbon, nanofoam, exhibited ferromagnetism.
	www.hallencyclopedia.com /Ferromagnetism (1052 words)

	Ferromagnetism
		Ferromagnetic materials exhibit a long-range ordering phenomenon at the atomic level which causes the unpaired electron spins to line up parallel with each other in a region called a domain.
		Ferromagnetism manifests itself in the fact that a small externally imposed magnetic field, say from a solenoid, can cause the magnetic domains to line up with each other and the material is said to be magnetized.
		When ferromagnetic materials are used in applications like an iron-core solenoid, the relative permeability gives you an idea of the kind of multiplication of the applied magnetic field that can be achieved by having the ferromagnetic core present.
	hyperphysics.phy-astr.gsu.edu /hbase/solids/ferro.html (1076 words)

	Theory
		However, due to the ferromagnetic exchange interaction, there is a difference between the number of spin up and spin down electrons in the conduction sub-bands of ferromagnetic materials.
		Therefore, the probability of an electron being scattered when it passes into a ferromagnetic conductor depends upon the direction of its spin and the direction of the magnetic moment of the layer.
		The resistance of two thin ferromagnetic layers separated by a thin non-magnetic conducting layer can be altered by changing whether the moments of the ferromagnetic layers are parallel or antiparallel.
	members.tripod.com /majidalhasani/Theory.htm (360 words)

	Ferromagnetism (Site not responding. Last check: 2007-11-02)
		Historically, the term "ferromagnet" was used for any material that could exhibit spontaneous magnetization: a net magnetic moment in the absence of an external magnetic field.
		More recently, however, different classes of spontaneous magnetization have been identified when there is more than one magnetic ion per primitive cell of the material, leading to a stricter definition of "ferromagnetism" that is often used to distinguish it from ferrimagnetism.
		Ferromagnetic metal alloys whose constituents are not themselves ferromagnetic in their pure forms are called Heusler alloys, named after Fritz Heusler.
	www.abitabouteverything.com /files/f/fe/ferromagnetism.html (1282 words)

	[No title]
		Ferromagnetism and the Curie temperature were explained by Weiss in terms of a huge internal field, the Ômolecular fieldÕ proportional to the magnetization.
		The origin of the internal field Hi is the exchange interaction, which reflects the electrostatic Coulomb repulsion of electrons on neighbouring atoms and the Pauli principle, which forbids two electrons from entering the same quantum state.
		The principal exchange mechanism in ferromagnetic and antiferromagnetic metals involves direct overlap of the partly-localized atomic orbitals of adjacent atoms.
	www.maths.tcd.ie /~pwalsht/WEBpdf/3015/3015-6.doc (2918 words)

	ScienceDaily: Chemistry (Site not responding. Last check: 2007-11-02)
		Most central and traditional to chemistry is the interaction of one substance with another such as in a chemical reaction where one substance or substances is transformed into another.
		The structure of the world we commonly experience and the properties of the matter we commonly interact with are determined by properties of chemical substances and their interactions.
		Biochemistry is the study of the chemicals, chemical reactions and chemical interactions that take place in living organisms.
	www.sciencedaily.com /encyclopedia/chemistry (3829 words)

	Junichiro Kono Laboratory
		The interaction of free carriers with localized spins plays an important role in a variety of magnetic and many-body phenomena in metals.
		One of the open questions is the nature of the carriers mediating the exchange interaction between Mn ions, i.e., whether they reside in the impurity band (d-like), the delocalized valence bands (p-like), or some type of mixed states.
		CR is a direct and accurate method for determining the effective masses of carriers (i.e., the curvature of the energy dispersion) and therefore the nature of the carrier states.
	www-ece.rice.edu /~irlabs/ferromagnetic.htm (1641 words)

	[No title]
		If the ferromagnetic phase forms the domain wall structures, the p-wave superconducting phase coherence is established in each domain and the anisotropic superconducting domains are coupled by the Josephson coupling.
		Presumably, the strong electron-phonon interaction and the ferromagnetic interaction lead to the p-wave superconducting condensation in manganese oxides.
		The apparent finite resistivity may be caused by the domain wall structures of the ferromagnetic phase, the coexisting minority spin electrons, the canted phase, and the possible existence of the FM and AF microdomains.
	www.ma.utexas.edu /mp_arc/papers/98-608 (3252 words)

	\"Linear anisotropy\" of magnetic susceptibility? - Advanced Physics Forums
		Ferromagnetic exchange interaction exists between atoms X. Atoms X have a spin-orbit coupling.
		If you add that the spin of atoms X couples (interaction energy) with the orbitals of the atoms X, then you see immediately that there should be a preferential direction AND orientation for the spin of atom X in term of energy.
		My argument was that, while the exchange interaction remains unchanged, the spin-orbit interaction has changed: because the orbitals are not symetric for that mirror transformation.
	www.advancedphysics.org /forum/showthread.php?t=275 (1100 words)

	ScienceWeek
		Furthermore, in spin valves composed from one ferromagnetic and one FEM layer, one of the layers would no longer need to be pinned if electric writing and magnetic reading were used.
		The authors demonstrate this principle for ferromagnetic cobalt nanoparticles of about 4 nm in diameter that are embedded in either a paramagnetic or an antiferromagnetic matrix.
		hole-induced ferromagnetism: In this context, a "hole" is an independently translocatable positively charged virtual particle produced by a translocated electron in a crystal semiconductor lattice, and the conductivity of the semiconductor is based on the mobility of both electrons and holes.
	scienceweek.com /2003/sw030808-2.htm (2489 words)

	[No title]
		We first discuss the ferromagnetic Heisenberg model at $T=0$ and finally extend our analysis to general spin hamiltonians for the same class of ferromagnetic ground states.
		Since magnetism is a purely quantum mechanical effect of interacting spin systems we clearly have to formulate a quantum mechanical model \cite{spitzer96}.
		We use the general ferromagnetic Heisenberg-Kac hamiltonian, which is motivated by the mean-field structure of (\ref{l2}).
	www.ma.utexas.edu /mp_arc/papers/99-329 (1797 words)

	High-Spin Building Blocks for Molecule-Based Magnets with Ferromagnetic Interaction based on Double Exchange
		In order to build a new class of molecular based magnets, molecular building blocks (synthons) which allow for strong ferromagnetic interactions between their paramagnetic centers are needed.
		This research project is based on the concept of double exchange which is known to propagate strong ferromagnetic interactions in mixed valence systems.
		The possibility of a switching behaviour of the magnetic and electrical properties is given by the metal-to-metal charge transfer absorption which corresponds to an excitation into a localized electronic state without ferromagnetic interactions and electrical conductivity.
	www.dfg.de /gepris/nachweise/233238.html (232 words)

	Magnetic interactions and the co-operative Jahn-Teller effect in KCuF3
		Because of the small overlap in the orbitally-ordered plane, the difference in kinetic energy between the AF2 and ferromagnetic phases is relatively small, and the dominant contribution to the energy difference is the additional electron-nuclear attraction in the ferromagnetic phase.
		In the ferromagnetic state, the contraction of majority (alpha) spin density on the F1 fluorine ion (centre left and centre right of the figure) is very large relative to that of the beta spin density.
		For antiferromagnetic superexchange contacts, the lowering of kinetic energy is the dominant contribution, while in the equivalent ferromagnetic interaction in orbitally-ordered planes, the electron-nuclear repulsion predominates.
	www.tcm.phy.cam.ac.uk /~mdt26/kcuf3/kcuf3.html (5319 words)

	PASPS III Conference: Poster Session
		Note that the spontaneous magnetization and the ferromagnetic Curie temperature increased with increasing hole concentration.
		Hence the weakly localized hole gives rise to the long-range ferromagnetic interaction between Mn ions although the complete localization of holes disturbs the ferromagnetism.
		In a magnetic field large enough to align the spontaneous magnetization in the direction of the applied field the measured resistance should oscillate simultaneously with a period of twice angle between the current direction and the magnetization as the field rotated.
	www.sainc.com /pasps3/agendaposterView.asp?paperID=146 (333 words)

	Research in the AG Kuch
		The latter is termed "exchange bias", and is frequently applied in magnetoresistive devices to manipulate or pin the magnetization direction of ferromagnetic layers in a multilayered stack.
		The magnetic interaction with an adjacent ferromagnetic film is studied by MOKE, XMCD, MLD, and PEEM.
		Using ferromagnetic resonance (FMR) in ultra-high vacuum we try to identify the relevant mechanisms for the damping of the magnetization precession in ultrathin films and multilayers.
	www.physik.fu-berlin.de /~ag-kuch/research.html?print (807 words)

	Session V18 - Semiconductors VIII: Magnetic Properties and Magnetic Semiconductors.
		We study the interaction between coherently-precessing electron spins and localized moments in semiconductors using pump-probe optical spectroscopy.(J.M. Kikkawa and D.D. Awschalom, Science (2000).) The frequency of electron Larmor precession obtained in measurements of time-resolved Faraday rotation serves as a magnetometer of the effective magnetic field experienced by electrons in n-type GaAs.
		Our theory is based on a picture in which the ferromagnetism is due to long-range interactions between Mn spins mediated by spin-polarized itinerant holes which interact antiferromagnetically with the localized spins.
		When subband mixing due to exchange interactions between localized magnetic moments and itinerant electrons is neglected, the dependence of the critical temperature and spontaneous magnetization on magnetic impurity concentration, exchange coupling, and the geometry of the system can be obtained analytically.
	flux.aps.org /meetings/YR00/MAR00/abs/S8170.html (2224 words)

	Sashi Satpathy Control of Magnetism in the Dilute Magnetic Semiconductors
		One is by increasing the carrier concentration by putting the magnetic atoms at the interface between two wurtzite semiconductors, where a two-dimensional hole gas (2DHG) forms because of the spontaneous polarization difference between the two crystals.
		The increased carrier concentration strengthens the ferromagnetic interaction between the Mn moments.
		The effect will be illustrated by examining a model Hamiltonian that includes the kinetic energy and the Coulomb interaction terms and the coupling of the carriers to light.
	www.uic.edu /casp/depts/phys/news/talks/colloquium/display.asp?ID=33 (236 words)

	Ferromagnetic semiconductor heterostructures
		This coupling gives rise to strong indirect exchange interactions between the localized moments as well as to giant spin-splittings of the electronic states, which is proportional to magneisation of the spins.
		Because of the large density of states and spin-dependent hybridisation between anion p and magnetic d states, the carrier-mediated spi-spin interaction is particularly strong in the presence of the holes in tetrahedrally coordinated DMS.
		Since ferromagnetic DMS combine intricate properties of charge-transfer insulators nd strongly correlated disordered metals with the physics of defect and band states in heavily doped semiconductors, despite important advances in theoretical understanding of these systems, their description from first principles may take some time.
	www.europhysicsnews.com /full/24/article5/article5.html (2269 words)

	Theses from Uppsala University : 2098 - Magnetism of manganites, semiconductors and spin glasses
		Due to random distribution of manganese in a Ag(Mn) alloy, competing ferromagnetic and antiferromagnetic interaction appears, yielding magnetic frustration and the appearance of a spin glass phase at low temperature.
		For an optimum doping x, a ferromagnetic order is established, and large changes of their electrical resistance with an applied magnetic field are observed; a magnetoresistance which can be tailored by adding oriented grain boundaries in thin films of these materials.
		The Manganese appears in the system as Mn and Mn, and both ferromagnetic and antiferromagnetic interaction is mediated by the charge carriers along the Mn-O-Mn bonds of the perovskite structure.
	publications.uu.se /theses/abstract.xsql?dbid=2098 (373 words)

	Research Area: Magnetic Materials
		We have recently suggested that a vibrationally induced modification of the spin-orbit interaction may be an important interaction.
		This suggests a competition between two interactions: a weak antiferromagnetic interaction due to superexchange, and a ferromagnetic interaction due to an indirect exchange mechanism mediated by free carriers.
		To help understand the origins of ferromagnetism in this material, we used density-functional theory to compute the effective coupling strength between Mn spins as a function of their separation (see "Further Reading" below).
	cst-www.nrl.navy.mil /ResearchAreas/MagneticMaterials (1053 words)

	[No title]
		Over the past few decades an understanding has developed that the collective properties of the many strongly interacting particles comprising condensed matter systems are by no means a simple consequence of the basic laws of interactions between them, so that exotic new phenomena, such as new phases of matter, continue to be discovered.
		One is the double-exchange interaction which gives rise to ferromagnetic interaction between adjacent Mn ions.
		The giant ferromagnetic Hall effect in the cobaltites may be used as sensitive magnetometers for operation at temperatures significantly higher than liquid helium temperatures.
	www.pma.caltech.edu /GSR/condmat.html (4242 words)

	Top20Chemistry.com - Online Directory for Chemistry Education.
		Because of the diversity of matter, which is mostly in the form of atoms, chemists often study how atoms of different chemical elements interact to form molecules and how molecules interact with each other.
		More central to chemistry is the interaction of matter with matter such as in the classic chemical reaction where chemical bonds are broken and made, forming new molecules.
		The structure of the world we commonly experience and the properties of the matter we commonly interact with are determined by the nature of this matter on the chemical level.
	www.top20chemistry.com (2302 words)

	The Quantum Pontiff » Oldschool, Contradiction, and a Strawman
		They use the Curie-Weiss (CW) model of a ferromagnet, which is not exactly realistic, but captures (for ferromagnetics of high enough dimension) much of the essential ideas of real ferromagnets.
		The energy of a particular configuration in the CW model is given by negative of the quantity of the total magentization squared times some arbitrary coupling constant.
		Ferromagnetic Ising interactions produce an energetically favorable condition to alligning the two spins involved in the interaction.
	dabacon.org /pontiff/?p=1217 (2384 words)

	Magnetic and Electrical Properties of ... (Site not responding. Last check: 2007-11-02)
		The Mn NMR spectra associated with Mn and Mn ions were observed in specimens having x smaller than 0.175, while motionally narrowed Mn spectra were observed where the values of x were 0.2 or 0.3.
		All the experimental results could be qualitatively explained by postulating that the d holes at the sites around Ca ions contribute to both the electrical conduction and the magnetic interaction.
		The ferromagnetic interaction induced by mobile d holes can not be ascribed to the double-exchange interaction, if this interaction has the usual form bcos(
	domino.research.ibm.com /tchjr/journalindex.nsf/0b9bc46ed06cbac1852565e6006fe1a0/786487439c0e483285256bfa0068409a?OpenDocument (168 words)

	Spins Project, Yazdani Group, Princeton (Site not responding. Last check: 2007-11-02)
		One of the most fascinating possibilities is the prospect that single spins, spin-clusters, and spin-based nanodevice structures may be model quantum-mechanical systems for understanding the processes of quantum entanglement and quantum decoherence.
		We are performing a variety of experiments to understand the nature of these unusually shaped electronic states and their interactions with each other.
		As) atom by atom and probe their interactions was recently highlighted as the cover article in the July 27, 2006 issue of Nature [3].
	wwwphy.princeton.edu /~yazdaniweb/spins.php (501 words)

	Frank Krueger \| publications
		The magnetic excitations are dominated by ferromagnetic exchange parameters revealing a nearly-one dimensional character at high energies.
		The nearest neighbor ferromagnetic interaction in La$_{1/2}$Sr$_{3/2}$MnO$_4$ is significantly larger than the one in the metallic ferromagnetically ordered manganites.
		The large ferromagnetic interaction in the charge/orbital ordered phase appears to be essential for the capability of manganites to switch between metallic and insulating phases.
	www.lorentz.leidenuniv.nl /~krueger/publications.html (733 words)

	SCMTALK Page 21
		In the ferromagnetic case, the 'contraction' of the up-spin density on the bridging fluorine is very large compared to that of the down-spin density.
		The 'closer average confinement' of up-spin electrons on the F ion means that the kinetic energy is much larger in the ferromagnetic case.
		=0.5), the magnetic interaction is antiferromagnetic, but not as much as up the c-axis, because there is still some residul orbital ordering caused by direct electrostatic interactions between the coppers (so the ordering is not completely lattice driven).
	www.tcm.phy.cam.ac.uk /~mdt26/tmo/page21.html (556 words)

	copper nickel magnetism (Site not responding. Last check: 2007-11-02)
		To put it simpistically, the interaction between a Ni-atom and a Cu-atom is not a ferromagnetic interaction.
		For a ferromagnetic interaction between 2 atoms, you must have the right extent of orbital overlap - and this depends on the shape of the valence wavefunctions as well as the separation between atoms.
		By making some of the near-neighbor interactions be paramagnetic instead of ferromagnetic, you are reducing the magnetization.
	www.physicsforums.com /showthread.php?t=90082 (213 words)

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