|MadSci Network: Physics|
Hello, Kevin Diamagnetism is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field. It is the result of changes in the orbital motion of electrons. Applying a magnetic field creates a magnetic force on a moving electron in the form of F = Qv × B. This force changes the centripetal force on the electron, causing it to either speed up or slow down in its orbital motion. This changed electron speed modifies the magnetic moment of the orbital in a direction opposing the external field. Consider two electron orbitals; one rotating clockwise and the other counterclockwise. An external magnetic field into the page will make the centripetal force on an electron rotating clockwise increase, which increases its moment out of the page. That field would make the centripetal force on an electron rotating counterclockwise decrease, decreasing its moment into the page. Both changes oppose the external magnetic field into the page. However, the induced magnetic moment is very small in most everyday materials. Fritz London and Heinz London developed the theory that the exclusion of magnetic flux is brought about by electrical "screening currents" that flow at the surface of the superconducting metal and which generate a magnetic field that exactly cancels the externally applied field inside the superconductor. These screening currents are generated whenever a superconducting metal is brought inside a magnetic field. This can be understood by the fact that a superconductor has zero electrical resistance, so that "eddy currents", induced by the motion of the metal inside a magnetic field, will not decay. Fritz, at the Royal Society in 1935, stated that the thermodynamic state would be described by a single wave function. http://en.wikipedia.org/wiki/Diamagnetic http://en.wikipedia.org/wiki/Bismuth http://en.wikipedia.org/wiki/Superdiamagnetism Magnons http://en.wikipedia.org/wiki/Magnon Thanks Brian D. Prater Cavetronics Labs
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