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Topic: Ferromagnetism


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  Ferromagnetism
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.
But in ferromagnetic materials the permeability may be very large and it is convenient to characterize the materials by a relative permeability.
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)

  
  Ferromagnetism -   (Site not responding. Last check: )
Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism.
The property of ferromagnetism is due to the direct influence of two effects from quantum mechanics: spin and the Pauli exclusion principle.
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.
www.i-encyclopedia.com /index.php/Ferromagnetism   (937 words)

  
 Ferromagnetism - Wikipedia, the free encyclopedia
Ferromagnetic metal alloys whose constituents are not themselves ferromagnetic in their pure forms are called Heusler alloys, named after Fritz Heusler (1903).
In a ferromagnet, however, they tend to align in the same direction because of the Pauli principle: two electrons with the same spin state cannot lie at the same position, and thus feel an effective additional repulsion that lowers their electrostatic energy.
As the temperature increases, thermal oscillation, or entropy, competes with the ferromagnetic tendency for dipoles to align.
en.wikipedia.org /wiki/Ferromagnetic   (1056 words)

  
 Ferromagnetism   (Site not responding. Last check: )
Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of thestrongest forms of magnetism.
The property of ferromagnetism is due to the direct influence of two effects from quantum mechanics : spin and the Pauli exclusion principle.
In a ferromagnet, however, they tend to align in the samedirection because of the Pauli principle: two electrons with the same spin cannot lie at the same position, and thus feel aneffective additional repulsion that lowers their electrostatic energy.
www.therfcc.org /ferromagnetism-20852.html   (901 words)

  
 Researchers Succeed in Inducing Ferromagnetism in High-k Dielectric Materials (Update)
Observation of high temperature ferromagnetism in lightly doped high-k dielectric materials with giant magnetic moment and such a high transition temperature is remarkable and represents a groundbreaking step in Spintronics.
Ferromagnetic metals (such as Fe, Ni etc) which were conventionally used for injecting spin polarized carriers in semiconducting transport medium, result in very low degree of spin polarization of injected carriers which is not sufficient for reliable device operation in most of the applications.
Discovery of high temperature ferromagnetism in dielectric films pave the way for the realization of novel spin filters to be used in actual spintronic devices.
www.physorg.com /news63964662.html   (917 words)

  
 Ferromagnetism Summary
Ferromagnetism is the "normal" form of magnetism which most people are familiar with, as exhibited in horseshoe magnets and refrigerator magnets, for instance.
The property of ferromagnetism is due to the direct influence of two effects from quantum mechanics: spin and the Pauli exclusion principle.
As the temperature increases, thermal oscillation, or entropy, competes with the ferromagnetic tendency for dipoles to align.
www.bookrags.com /Ferromagnetism   (2297 words)

  
 Ferromagnetism   (Site not responding. Last check: )
Ferromagnetism is a phenomenon by which a can exhibit a spontaneous magnetization and is of the strongest forms of magnetism.
In a ferromagnet however they to align in the same direction because of the Pauli principle: electrons with the same spin cannot lie the same position and thus feel an additional repulsion that lowers their electrostatic energy.
The study of ferromagnetic phase transitions especially the simplified Ising spin model had an important impact the development of statistical physics.
www.freeglossary.com /Ferromagnetic   (864 words)

  
 ferromagnetism - Hutchinson encyclopedia article about ferromagnetism   (Site not responding. Last check: )
Form of magnetism that can be acquired in an external magnetic field and usually retained in its absence, so that ferromagnetic materials are used to make permanent magnets.
A ferromagnetic material may therefore be said to have a high magnetic permeability and susceptibility (which depends upon temperature).
Ultimately, ferromagnetism is caused by spinning electrons in the atoms of the material, which act as tiny weak magnets.
encyclopedia.farlex.com /ferromagnetism   (201 words)

  
 ferromagnetism
Form of magnetism that can be acquired in an external magnetic field and usually retained in its absence, so that ferromagnetic materials are used to make permanent magnets.
A ferromagnetic material may therefore be said to have a high magnetic permeability and susceptibility (which depends upon temperature).
Ultimately, ferromagnetism is caused by spinning electrons in the atoms of the material, which act as tiny weak magnets.
www.tiscali.co.uk /reference/encyclopaedia/hutchinson/m0031086.html   (266 words)

  
 Ferromagnetism on Co- and Mn-Doped ZnO
For Co-doped ZnO, there is some evidence that the observed ferromagnetism may be due to Co precipitates instead of carrier-mediated exchange in the ZnO matrix.
Macroscopic Co precipitates would be ferromagnetic with a bulk Curie temperature of 1382 K. However, at ~3.6 nm in diameter, the Co nanocrystals should exhibit superparamagnetic behavior.
Low temperature ferromagnetism is observed, while the samples do not exhibit magnetic hysteretic behavior at room temperature.
www.mse.ufl.edu /~spear/recent_papers/CoZnO/CoZnO.htm   (2409 words)

  
 What is the difference between paramagnetism and ferromagnetism?
Ferromagnetism refers to materials (such as iron and nickel) that can retain their magnetic properties when the magnetic field is removed.
In ferromagnetic materials, however, the electron fields in the atoms do not cancel out, so they exhibit a long-range ordering phenomenon at the atomic level, which causes unpaired electron spins to line up parallel with each other in a region called a domain.
Ferromagnetic materials will respond mechanically to an impressed magnetic field, changing length slightly in the direction of the applied field.
www.physlink.com /Education/AskExperts/ae595.cfm   (591 words)

  
 Encyclopedia: Ferromagnetism
The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units.
In physics, the Curie point, or Curie temperature, is the temperature above which a ferromagnet loses its ferromagnetic ability to possess a net (spontaneous) magnetization in the absence of an external magnetic field.
Paramagnetism is the tendency of the atomic magnetic dipoles, due to quantum-mechanical spin as well as electron orbital angular momentum, to align with an external magnetic field.
www.nationmaster.com /encyclopedia/Ferromagnetism   (2426 words)

  
 Metallic ferromagnetism   (Site not responding. Last check: )
Ferromagnetism first appears in the periodic table in the transition elements iron, cobalt, and nickel, which appear consecutively at the right end of the first row of transition metals.
The ferromagnetic state in these metals persists up the "Curie temperature", which is 600 K or higher (when the macroscopic magnetization vanishes).
This helps to explain why ferromagnetism appears first in the transition metals with more than half-filled d-band: these have a particularly large value for the level density (since there are 5 d-subbands and as we move rightward in the periodic table the d-bands narrow).
carini.physics.indiana.edu /P616/lecture-notes/ferromagnetism.html   (568 words)

  
 metallic ferromagnetism
In the conventional view of metallic ferromagnetism, it is driven by 'exchange energy' between conduction electrons in rigid bands.
We have proposed an alternative way to understand the origin of ferromagnetism in metals, namely that it is driven by effective mass reduction, or equivalently band broadening, or 'undressing' of carriers, that occurs upon spin polarization.
Superconductivity and Ferromagnetism from Effective Mass Reduction, presented at the 6th International Conference on Materials and Mechanisms of Superconductivity, Houston, February 2000, Physica C 341-348, 211 (2000).
physics.ucsd.edu /~jorge/ferro.html   (181 words)

  
 Ferromagnetism   (Site not responding. Last check: )
Ferromagnetic materials are materials which can be permanently magnetized upon application of an external magnetic field.
If the temperature of a ferromagnetic material is raised past a certain point (called the Curie temperature) the material abruptly loses its permanent magnetization and becomes simply paramagnetic[1].
Consider a ferromagnetic material which is originally unmagnetized (point a).
www.ee.washington.edu /conselec/CE/kuhn/taperecord/ferro.htm   (457 words)

  
 Magnetic Resonance TIP - MRI Database : 'Ferromagnetism'
These materials include magnets, and various objects one might find in a patient, such as aneurysm clips, parts of pacemakers, shrapnel, etc. These materials have a large positive magnetic susceptibility, i.e., when placed in a magnet field, the field strength is much stronger inside the material than outside.
Ferromagnetic materials are also characterized by being made up of clusters of 10
A contrast agent, which due to their ferromagnetism produce local field inhomogeneities and hence visible image alterations in the tissues where they are present.
www.mr-tip.com /serv1.php?type=db1&dbs=Ferromagnetism   (338 words)

  
 Ferromagnetism
Ferromagnetic materials are used either to channel magnetic flux (e.g.
Thus, it is vitally important that a permanent magnet should possess both a large remanence and a large coercivity.
As will become clear later on, it is generally a good idea for the ferromagnetic materials used to channel magnetic flux around transformer circuits to possess small remanences and small coercivities.
farside.ph.utexas.edu /~rfitzp/teaching/em/lectures/node75.html   (479 words)

  
 Strain-Induced Ferromagnetism in Intermetallic Compounds
The strain-induced ferromagnetism in lightly-strained FeAl appears to arise mostly from APB tubes.
There are two sources of ferromagnetism in off-stoichiometric FeAl, that from the constitutional disorder from anti-site Fe atoms and that from APB tubes.
An APB tube encloses a region in which the lattice is displaced by an APB displacement vector with respect to the lattice outside the tube.
www.dartmouth.edu /~ianbaker/ferromag/ferromag.html   (634 words)

  
 ferromagnetism and superconductivity
Within a simple model Hamiltonian, both superconductivity and metallic ferromagnetism can be understood as arising from lowering of kinetic energy as the ordered state develops, due to a reduction in the carriers effective mass, or equivalently, a bandwidth expansion.
Experimental manifestation of this physics has been detected in both high Tc superconductors and large magnetoresistance ferromagnets, as an anomalous transfer of spectral weight in optical absorption from high to low frequencies as the ordered state develops.
It is proposed that this general principle is common to the essential physics of superconductivity and ferromagnetism in nature, and hence that these effects in optical properties, although often smaller in magnitude, should exist in all superconductors and metallic ferromagnets.
physics.ucsd.edu /~jorge/abstracts/ferrosc.html   (139 words)

  
 Using Ferromagnetism and Giant Magnetoresistance To Sense IR
Using Ferromagnetism and Giant Magnetoresistance To Sense IR Using Ferromagnetism and Giant Magnetoresistance To Sense IR Proposed sensors and imaging devices could operate at room temperature.
The ferromagnetic layer would be separated from the GMR layers by a nonmagnetic layer with a thickness chosen to provide both magnetic coupling and sufficient thermal insulation to enable the temperature of the ferromagnetic layer to rise appreciably upon exposure to infrared radiation.
One of the advantages of both ferromagnetic materials and GMR sensors is that they can be engineered to operate at a chosen temperature with acceptably high sensitivity.
www.nasatech.com /Briefs/Mar01/NPO20929.html   (478 words)

  
 Diestrich's Homepage
Ferromagnetism within the periodic Anderson model: A new approximation scheme
Influence of spin-flip scattering on the stability of ferromagnetism in a two-band Hubbard model
Dynamic mean-field study of ferromagnetism in the periodic Anderson model
tfk.physik.hu-berlin.de /~dmeyer   (180 words)

  
 Physics Today September 2001
Although the observations of coexistent ferromagnetism and superconductivity are barely two years old, theorists had anticipated the discovery more than 20 years ago.
But, argue Kirkpatrick and company, the longitudinal fluctuations on the ferromagnetic side are actually larger than on the paramagnetic side thanks to coupling with transverse fluctuations (fluctuations in the spins' direction).
Even iron itself, the archetypal ferromagnet, has recently been found to be a superconductor, albeit under such high pressure that it ceases to be ferromagnetic.
www.physicstoday.org /pt/vol-54/iss-9/p16.html   (1377 words)

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