COLLECTIVE PINNING THEORY AND MAGNETIC PINNING INTERACTION IN NBTI

The present work shows that vortex pinning behaviour in NbTi is primar ily a magnetic interaction. The vortex lattice under the action of pin ning centres deforms and a vortex lattice dislocation(VLD) is stablish ed. Using a Modified Collective Pinning Theory (MCPT), it can be shown that when the quantity of VLD is maximum, the magnetic interaction is larger than the core pinning interaction. Application of MCPT to arti ficial pinning centre (APC) composite shows complete agreement between theoretical and experimental results for the reduced pinning force de nsity curve as a function of reduced magnetic field (F(p)xb).