Observation of Dynamic Interaction of Vortices with Pinning
Centers by Lorentz Microscopy
Tsuyoshi Matsuda,
Ken Harada,
Hiroto Kasai,
Osamu Kamimura,
Akira Tonomura
*
When a magnetic field penetrates a superconductor, it forms
lattices of thin filaments called magnetic vortices. If a current is
applied, these vortices move if not pinned down, destroying the
superconductivity. The spatiotemporal behavior of the vortices was
observed in a niobium film with a square lattice of defects made by ion
irradiation. The vortices formed a domain of lattices. When the
intensity of the applied magnetic field was decreased, the vortices
were driven out of the film across its edges; when the intensity was
increased, the vortices were driven into the film. The lattice
exhibited brief and intermittent flow in ``rivers'' along domain
boundaries. The rivers did not always flow along the same paths because
new lattice domain configurations emerged whenever the flow stopped.
Advanced Research Laboratory, Hitachi Ltd., Hatoyama, Saitama 350-03, Japan.
*
To whom correspondence should be addressed.
