Fig. 7.

Neutron scattering in perpendicular field geometry. In the perpendicular field geometry (Fig. 2b), rocking curves probe correlations in the plane of the vortices. a–d Rocking curves of the first order diffraction peak at four selected points in the phase diagram, collected with long counting times to afford high quality data for reverse Monte Carlo refinement. Backgrounds measured at zero field have been subtracted. Ordinate axes are normalised for comparison. In reverse Monte Carlo refinement, simulated vortices are displaced using a Monte Carlo method until the experimental rocking curve (circles) is reproduced (red lines). Black lines indicate instrument resolution. e Rocking curves of a and d on logarithmic axes. Dashed line is a guide showing an algebraic decay. Algebraic tails are expected from the Bragg glass picture. Gaussian fits (blue lines) are drawn for comparison