373 K Superconductors
We have shown data and demonstrations of the 373K Supercondcutors. The most popular demo is considered the levitation of supercondcutors in strong magnetic field. But frogs are also levitating in a strong magnet and it is not a Meisner effect. The correct descriptions of the Meisner effect usually mention that it is observed only if the magnets are not stronger than the first critical magnetic field Hc1, which for YBa2Cu3Ox type of superconductors is of the order of 250 Gs (25mT) for a Tc = 56 K ( Tc is different for different compositions of YBACUO). The comercial strong Nd based disk type magnets have a field, which in the center of the disk can be as high as 1.4T and it penetrates the superconductor in flux quanta -Abricosov Lattice. The force, which keeps it floating arises from a complicated set of induced currents and is not due to pure Meisner effect. For a typical Meisner effect -below the first critical field-one stable position of a disk shaped magnet above a superconductor is vertical on the superconductor. The system of surface currents in the superconductor could be described in a way similar to the currents produced by an image-magnetic disk with opposite magnetic moment inside a semi-infinite superconductor. Similarly a small flat magnet on top of a superconductor (high Hc1 case) stays vertical with its magnetic filed oriented parallel to the superconductor surface and not penetrating it. We again show below an illustrtion with such a composition of small Nd based disk magnets on top of varous superconductor disks and soon will show the video.
1.Manuscript.-arXiv:1603.01482v1 [physics.gen-ph] 4 Mar 2016.
2. Direct measurement of the upper critical field of a cuprate superconductor.-arXiv:1304.3856.