NEUTRON-DIFFRACTION STUDIES OF FLOWING AND PINNED MAGNETIC-FLUX LATTICES IN 2H-NBSE2

We report on detailed neutron diffraction studies of both pinned and m oving magnetic flux line lattices in 2H-NbSe2. For field-cooled, pinne d lattices, we are able to make a detailed quantitative comparison wit h the theory of Larkin and Ovchinnikov and find excellent agreement. I n studies of the dynamics, we find that the longitudinal correlation l ength of the vortex lattice increases substantially when it is depinne d and moving due to a current exceeding the critical current, and rema ins large when the lattice is repinned after turning the current off.