Precise Study of Vortex Structures in Nb by Small-Angle Neutron Scattering

The microscopic magnetic structure of a vortex in a Nb single crystal was investigated using small-angle neutron scattering by measuring higher order reflections. By fitting the experimental scattering intensities, the magnetic structure of a vortex can be represented by the London equation with an additional Gaussian factor due to the thermal displacement of vortices. The radius of a vortex (20.3 nm at 3.3 K) is somewhat smaller than the London penetration depth (λ L (0)=31.5–39.0 nm).