Meissner Effect


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Related to Meissner Effect: London equations, Cooper pairs

Meissner effect

The expulsion of magnetic flux from the interior of a superconducting metal when it is cooled in a magnetic field to below the critical temperature, near absolute zero, at which the transition to superconductivity takes place. It was discovered by Walther Meissner in 1933, when he measured the magnetic field surrounding two adjacent long cylindrical single crystals of tin and observed that at -452.97°F (3.72 K) the Earth's magnetic field was expelled from their interior. This indicated that at the onset of superconductivity they became perfect diamagnets. This discovery showed that the transition to superconductivity is reversible, and that the laws of thermodynamics apply to it. The Meissner effect forms one of the cornerstones in the understanding of superconductivity, and its discovery led F. London and H. London to develop their phenomenological electrodynamics of superconductivity. See Diamagnetism, Thermodynamic principles

The magnetic field is actually not completely expelled, but penetrates a very thin surface layer where currents flow, screening the interior from the magnetic field.

The Meissner effect is subject to limitations. Full diamagnetism is not observed in polycrystalline samples, and the effect is not observed in impure samples or samples with certain geometrics, such as a round flat disk, with the magnetic field parallel to the axis of rotation. See Superconductivity

Meissner Effect

 

the complete expulsion of a magnetic field from a metal conductor when it becomes superconductive (when the intensity of the applied magnetic field is less than the critical value Hc). The Meissner effect was first observed in 1933 by the German physicists W. Meissner and R. Oxenfeld. Partial “freezing” of the magnetic field in the superconductor—that is, incompleteness of the Meissner effect—is observed in insufficiently pure metals and especially in alloys.

Meissner effect

[′mīs·nər i‚fekt]
(solid-state physics)
The expulsion of magnetic flux from the interior of a piece of superconducting material as the material undergoes the transition to the superconducting phase. Also known as flux jumping; Meissner-Ochsenfeld effect.
References in periodicals archive ?
The Meissner Effect is one such phenomenon, where a magnet levitates above a superconductor.
Exposition: This section showcases the Meissner Effect, performed with a ceramic superconductor cooled with liquid nitrogen and a rare earth magnet.
Theory: The theory behind the Meissner Effect is explained, as well as the general theory regarding superconductors.
After this, the Exposition segment was shown, demonstrating the Meissner effect without explanation.
The Meissner effect is the base for superconductivity.
The exclusion of gravity by the hedge gluon force field as in the Meissner effect prevents the gravitational collapse into singularity.
Prochnow tries valiantly to use the simple electronic model to explain the six superconductor properties, including zero resistivity, the Meissner effect, crystal lattice structure, electron distance coherence, specific heat and electron isotope changes.
But because materials can experience a drop in resistance without being true superconductors, another test is necessary: measuring what's called the Meissner effect, the expulsion of a magnetic field from the material's interior.
All four of these criteria have been met in some of the new copper oxides at the 90 to 100 K range; zero resistivity and a partial Meissner effect have been seen at 225 K; partial resistivity has been seen at 290 K; and a drop in resistance and some other faint indications of superconductivity have been observed at 360 K, according to Paul C.
Therefore he was not able to apply the second standard test for superconductivity, the Meissner effect, in which a superconductor resists penetration by a magnetic field imposed from outside.
Chu of the University of Houston and his colleagues from the University of Houston an the University of Alabama at Huntsville were able to test for the Meissner effect in a sample that lost all resistance at 225 K (-54[deg.