Direct Observation of Vortex Dynamics in Superconducting Films with Regular Arrays of Defects
The microscopic mechanism of the matching effect in a superconductor, which manifested itself as the production of peaks or cusps in the critical current at specific values of the applied magnetic field, was investigated with Lorentz microscopy to allow direct observation of the behavior of vortices in a niobium thin film having a regular array of artificial defects. Vortices were observed to form regular and consequently rigid lattices at the matching magnetic field, at its multiples, and at its fractions. The dynamic observation furthermore revealed that vortices were most difficult to move at the matching field, whereas excess vortices moved easily.
K. Harada, O. Kamimura, H. Kasai, T. Matsuda, A. Tonomura, Advanced Research Laboratory, Hitachi, Ltd., Hatoyama, Saitama 350-03, Japan. V. V. Moshchalkov, Laboratorium voor Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium.
K
Harada
O
Kamimura
H
Kasai
T
Matsuda
A
Tonomura
VV
Moshchalkov