Date of Award

2007

Document Type

Thesis

Degree Name

Master of Science in Material Science Engineering (MSMatSE)

Department

Materials Science

First Advisor

Dr. Usama Al Khawaja

Second Advisor

Dr. Thab Obaidat

Third Advisor

Dr. Maamar Benkraouda,

Abstract

Superconductor materials that have no resistance to the flow of electricity are one of the last great frontiers of scientific discovery.

Superconductivity in these materials occurs particularly in the copper-oxide (CuO2) planes. However, since these materials are type-II superconductors, magnetic fields can penetrate these materials in quantized amounts of flux called vortices without completely destroying superconductivity, but producing some resistance, due to vortex motion. In order to overcome the resistance problem, vortices must be pinned to prevent their motion and hence eliminate the resistance.

In this work study we have performed extensive numerical simulations to study the effect of the size of pinning centres on the critical current density of driven vortex lattices interacting with square periodic arrays of pinning sites. This has been carried out at different temperatures and for several values of pinning strengths. We have solved the over damped equation of vortex motion taking into account the vortex-vortex repulsion interaction, the attractive vortex-pinning interaction, the thermal force, and the driving Lorentz force.

We have found that, while the critical current density increases with pinning size at high temperatures, it is almost independent of pinning size at low temperatures. We have also

found that increasing the size of the pinning centers suppresses the rate at which the critical current density decreases with temperature.

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