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 configurations of vortices inside the superconducting plate with pinning centers. The pictures of the magnetic flux distribution were obtained for cyclical changes of the external magnetic field at different temperatures and defective states of the superconductor. A sharp zone of zero magnetic field exists between the regions of magnetic fields with opposite sign. The zero field zone moves from the edges to the center of the superconductor when the external field changes. Authors called this phenomenon annihilation waves. The peculiarities of annihilation waves at different temperatures and defects concentrations have been investigated. The maps of the magnetic field distribution as well as the motion of the annihilation waves correlate with the static and dynamic images observed in magneto-optical and scanning Hall sensor experiments. 6 refs.