SANS Study of Edge-Contaminated Vortex States in a V$_{21at\% }$Ti Superconducting Alloy

In this talk, we report the first direct observation of edge-contaminated vortex matter using small angle neutron scattering (SANS). The vortex structures of Zero Field Cooled and Field Cooled states in a high-$\kappa $ superconducting alloy have been studied using SANS. In this sample FC states are partially ordered as shown by the coexistence of a diffuse scattering ring with two Bragg peaks. ZFC states are disordered at low fields and more disordered than FC states at all fields. For example, the ZFC vortex state at H=6 kOe gives a diffuse ring indicating an amorphous state. Upon further increasing the field, Bragg peaks emerge from the ring, indicating ordering. On increasing temperature from the disordered structure at 6 kOe, the ring gradually transforms into distinct peaks. The experiments were performed at the NIST Center For High Resolution Neutron Scattering (CHRNS).