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- Colossal_magnetoresistance abstract "Colossal magnetoresistance (CMR) is a property of some materials, mostly manganese-based perovskite oxides, that enables them to dramatically change their electrical resistance in the presence of a magnetic field. The magnetoresistance of conventional materials enables changes in resistance of up to 5%, but materials featuring CMR may demonstrate resistance changes by orders of magnitude.Initially discovered in mixed-valence perovskite manganites in the 1950s by G. H. Jonker and J. H. van Santen., a first theoretical description in terms of the double-exchange mechanism was given early on. In this model, the spin orientation of adjacent Mn-moments is associated with kinetic exchange of eg-electrons. Consequently, alignment of the Mn-spins by an external magnetic field causes higher conductivity. Relevant experimental work was done by Volger, Wollan and Koehler, and later on by Jirak et al. and Pollert et al.However the double exchange model did not adequately explain the high insulating-like resistivity above the transition temperature. In the 1990s, work by R. von Helmolt et al. and Jin et al. initiated a large number of further studies. Although there is still no complete understanding of the phenomenon, there is a variety of theoretical and experimental work providing a deeper understanding of the relevant effects.One prominent model is the so-called half-metallic ferromagnetic model, which is based on spin-polarized (SP) band structure calculations using the local spin-density approximation (LSDA) of the density functional theory (DFT) where separate calculations are carried out for spin-up and spin-down electrons. The half-metallic state is concurrent with the existence of a metallic majority spin band and a nonmetallic minority spin band in the ferromagnetic phase.This model is not the same as the Stoner Model of itinerant ferromagnetism. In the Stoner model, a high density of states at the Fermi level makes the nonmagnetic state unstable. With SP calculations on covalent ferromagnets, the exchange-correlation integral in the LSDA-DFT takes the place of the Stoner parameter. The density of states at the Fermi level does not play a special role. A significant advantage of the half-metallic model is that it does not rely on the presence of mixed-valency as does the double exchange mechanism and it can therefore explain the observation of CMR in stoichiometric phases like the pyrochlore Tl2Mn2O7. Microstructural effects have also been investigated for polycrystalline samples and it has been found that the magnetoresistance is often dominated by the tunneling of spin polarized electrons between grains, giving rise to an intrinsic grain-size dependence to the magnetoresistance.A fully quantitative understanding of the CMR effect has been elusive and it is still the subject of current research activities. Early prospects of great opportunities for the development of new technologies have not yet come to fruition.".
- Colossal_magnetoresistance wikiPageExternalLink 12.
- Colossal_magnetoresistance wikiPageExternalLink index.html.
- Colossal_magnetoresistance wikiPageExternalLink news106576042.html.
- Colossal_magnetoresistance wikiPageID "875676".
- Colossal_magnetoresistance wikiPageLength "7560".
- Colossal_magnetoresistance wikiPageOutDegree "14".
- Colossal_magnetoresistance wikiPageRevisionID "681421870".
- Colossal_magnetoresistance wikiPageWikiLink Category:Magnetic_ordering.
- Colossal_magnetoresistance wikiPageWikiLink Category:Quantum_electronics.
- Colossal_magnetoresistance wikiPageWikiLink Category:Spintronics.
- Colossal_magnetoresistance wikiPageWikiLink Density_functional_theory.
- Colossal_magnetoresistance wikiPageWikiLink Double-exchange_mechanism.
- Colossal_magnetoresistance wikiPageWikiLink Edmund_Clifton_Stoner.
- Colossal_magnetoresistance wikiPageWikiLink Electrical_resistance.
- Colossal_magnetoresistance wikiPageWikiLink Electrical_resistance_and_conductance.
- Colossal_magnetoresistance wikiPageWikiLink Giant_magnetoresistance.
- Colossal_magnetoresistance wikiPageWikiLink Magnetic_field.
- Colossal_magnetoresistance wikiPageWikiLink Magnetoresistance.
- Colossal_magnetoresistance wikiPageWikiLink Manganese.
- Colossal_magnetoresistance wikiPageWikiLink Oxide.
- Colossal_magnetoresistance wikiPageWikiLink Perovskite.
- Colossal_magnetoresistance wikiPageWikiLinkText "CMR".
- Colossal_magnetoresistance wikiPageWikiLinkText "Colossal magnetoresistance".
- Colossal_magnetoresistance wikiPageWikiLinkText "colossal magnetoresistance".
- Colossal_magnetoresistance hasPhotoCollection Colossal_magnetoresistance.
- Colossal_magnetoresistance wikiPageUsesTemplate Template:Dead_link.
- Colossal_magnetoresistance wikiPageUsesTemplate Template:Reflist.
- Colossal_magnetoresistance subject Category:Magnetic_ordering.
- Colossal_magnetoresistance subject Category:Quantum_electronics.
- Colossal_magnetoresistance subject Category:Spintronics.
- Colossal_magnetoresistance hypernym Property.
- Colossal_magnetoresistance type Building.
- Colossal_magnetoresistance type Mechanic.
- Colossal_magnetoresistance type Physic.
- Colossal_magnetoresistance comment "Colossal magnetoresistance (CMR) is a property of some materials, mostly manganese-based perovskite oxides, that enables them to dramatically change their electrical resistance in the presence of a magnetic field. The magnetoresistance of conventional materials enables changes in resistance of up to 5%, but materials featuring CMR may demonstrate resistance changes by orders of magnitude.Initially discovered in mixed-valence perovskite manganites in the 1950s by G. H. Jonker and J. H.".
- Colossal_magnetoresistance label "Colossal magnetoresistance".
- Colossal_magnetoresistance sameAs CMR-Effekt.
- Colossal_magnetoresistance sameAs Magnetorresistencia_colosal.
- Colossal_magnetoresistance sameAs مغناطومقاومت_عظیم.
- Colossal_magnetoresistance sameAs Magnétorésistance_colossale.
- Colossal_magnetoresistance sameAs Magnetorresistência_colossal.
- Colossal_magnetoresistance sameAs m.03ksth.
- Colossal_magnetoresistance sameAs Колоссальное_магнетосопротивление.
- Colossal_magnetoresistance sameAs Từ_điện_trở_siêu_khổng_lồ.
- Colossal_magnetoresistance sameAs Q1023887.
- Colossal_magnetoresistance sameAs Q1023887.
- Colossal_magnetoresistance sameAs 超巨磁阻效应.
- Colossal_magnetoresistance wasDerivedFrom Colossal_magnetoresistance?oldid=681421870.
- Colossal_magnetoresistance isPrimaryTopicOf Colossal_magnetoresistance.