Tuesday, 08/19/08

Session Title:	Flux Pinning and Dynamics II - Engineered Pinning Arrangements
Session Chairs:	Paul Barnes, Air Force Research Laboratory, Wright-Patterson AFB & Takanobu Kiss, Kyushu University
Paper Number:	2MPD09
Start Time:	10:00am
Session Type:	Poster

Flux pinning properties in superconducting Nb films with asymmetric artificial pinning centers J. He, N. Harada, N. Matsumura, H. Asada, H. Naitou, Yamaguchi University; T. Ishibashi, Nagaoka University of Technology; O. Miura, Tokyo Metropolitan University

It is known that asymmetric shape of the pinning centers induced significant asymmetries in the magnetic flux force and the distribution of the critical current density. In pervious studies, we have analyzed that the superconductor patterned with asymmetric pinning centers has a different asymmetric flux pinning properties from the superconductor patterned with symmetric pinning centers by theoretical calculation. In order to demonstrate it, two types of artificial pinning centers (APCs) with an area of 0.5 mm × 1.0 mm: symmetric groove-shaped APCs and asymmetric step-shaped APCs , have been introduced into the Nb films with an area of 0.5 mm × 2.0 mm by using the lithographic technique, respectively. The shift between the position where the magnetic flux density is the lowest and that where it is the highest was directly observed by using the magneto-optical (MO) imaging method. It is considered that the shift, which indicates an anisotropy of pinning force caused by the asymmetric conformation. In this paper, we investigated the anisotropy of the flux pinning properties by evaluating the distribution of the critical current density of specimens with asymmetric step-shaped APCs. The Nb film of 0.5 μm thickness was evaporated on an Al2O3 (1102) single crystalline substrate by the molecular beam evaporation (MBE) method and the periodical intervals of patterns is 5 μm.