The Meissner Effect, also known as magnetic focusing, is a phenomenon in which a superconductor expels all magnetic fields from its interior when it is cooled below its critical temperature.
The Meissner Effect occurs due to the formation of a superconducting state in which the electrons pair up and move without resistance. This state causes the expulsion of magnetic fields from the interior of the superconductor, creating a perfect diamagnet.
The Meissner Effect has various applications in technology, including in magnetic levitation, magnetic resonance imaging (MRI) machines, and particle accelerators. It is also used in the production of high-quality crystals and in the development of sensitive magnetometers.
The Meissner Effect is different from other types of magnetism, such as ferromagnetism and paramagnetism, because it only occurs in superconductors below their critical temperature. Unlike ferromagnets, superconductors do not retain any magnetic field after the external field is removed.
One limitation of the Meissner Effect is that it only occurs at very low temperatures. Another limitation is that it can only expel weak magnetic fields, and strong magnetic fields can cause the superconductor to lose its superconductivity. There is also ongoing research to understand and overcome the limitations of the Meissner Effect for further technological advancements.