Numerical simulation and experimental observation of magnetic flux distribution in high-temperature superconductors

A new procedure for the minimization of the free energy potential by means of Monte Carlo techniques has been used to calculate the equilibrium config urations of vortices inside the superconducting plate with pinning centres. The pictures of the magnetic flux distribution were obtained for cyclical changes of the external magnetic field at different temperatures and defect ive states of the superconductor. A sharp zone of zero magnetic field was f ound to exist between the regions of magnetic fields with opposite sign. It was shown that the zero field zone moves from the edges to the centre of t he superconductor when the external field changes. We called this phenomeno n 'annihilation waves'. The peculiarities of annihilation waves at differen t temperatures and defects concentrations have been investigated. The maps of the magnetic field distribution as well as the motion of the annihilatio n waves correlate well with the static and dynamic images which were observ ed in the our recent magneto-optical and scanning Hall sensor experiments.