SMALL-ANGLE NEUTRON-SCATTERING STUDY OF THE MAGNETIC FLUX-LINE-LATTICE IN SINGLE-CRYSTAL 2H-NBSE2

We report on a small angle neutron scattering study of the flux-line l attice in single crystal 2H-NbSe2. As the magnetic field is tilted awa y from the crystalline c axis, we find distortions in the flux lattice as would be expected for a mass anisotropy GAMMA = 10.1 +/- 0.9. Howe ver, we find that the lattice orientation is in disagreement with the predictions of both anisotropic London and Ginzburg-Landau theories. T he observed flux lattice orientation remains pinned to that of the cry stal lattice for the field orientations studied. The form factors can be quantitatively understood within the framework of Ginzburg-Landau c orrections to the London equations.