Browsing by Author "Kang, PC"

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Anisotropic pinning effect on a Nb thin film with triangular arrays of pinning sites
(2004-06-01)
Wu, TC
;
Kang, PC
;
Horng, L
;
Wu, JC
;
Yang, TJ
A superconducting Nb thin film with triangular arrays of pinning sites has been fabricated to investigate the commensurate vortex lattices. Vortex-vortex interactions in this pattern film make the observed anisotropy in the pinning properties. Periodic minima appear in the magnetoresistance curves at equal field intervals that can be associated with matching effect. The transport properties at near critical temperatures show anisotropic pinning properties related to the configuration of pinning centers. The critical current is depressed when the driving force is applied along the short diagonal in the rhombic unit cell of pinning array. It implies that the pinning potential along the short diagonal creates a moving channel of vortices in triangular arrays of defects. The pinned and interstitial vortices can be movable in an incommensurate vortex row and a straight unhindered one-dimensional path. (C) 2004 American Institute of Physics.
Pinning effects induced by periodic arrays of structural corrugations in Nb thin films
(2003-05-01)
Horng, L
;
Wu, JC
;
Kang, PC
;
Lin, PH
;
Wu, TC
Artificial vortex pinning arrays have been fabricated by electron-beam lithography in conjunction with reactive ion etching in Nb superconducting thin films in order to investigate flux pinning. Based on the structural corrugation in the Nb thin film, the square lattice of defects that act as pinning centers was created. A strong periodic pinning effect, as the vortex lattice matches the array of defects, can be observed in the evolution of resistivity and critical current with the applied magnetic fields in the mixed state of the Nb film, thus, revealing a synchronized pinning effect due to structural corrugation. This result is in agreement with the resistivity-temperature curves at matching fields and half-integer matching fields in which a crossover occurs for temperatures exceeding a certain threshold value. The phenomenon is related to the presence of the pinning structure at matching fields.
Vortex dynamics in Nb thin films with triangular potential
(2005-06-01)
Wu, TC
;
Kang, PC
;
Wu, JC
;
Horng, L
;
Yang, TJ
Triangular artificial antidot arrays in Nb superconducting thin films have been fabricated to investigate the flux pinning effect when the magnetic field is applied perpendicular to the film. The spacing of the defect is around 545 nm and the diameter of the defect is around 300 nm. Arrays of triangular lattice show anisotropic properties of pinning effect induced by the anisotropic structure. The vortex-vortex interaction force is stronger when the vortices move along the short axis in the rhombic unit cell and cause an overall higher normalized critical current.