Square to hexagonal symmetry transition of the flux line lattice in YNi₂B₂C for different field orientations

Using small-angle neutron scattering we have studied the magnetic flux line lattice in YNi2B2C with the field rotated 30(:) away from the crystalline c-axis. Previously we have reported on a square to hexagonal symmetry transition of the fluc line lattice below 1 kOe for H parallel to c. We find that the rotation of the field shifts the transition to higher fields in agreement with theoretical prediction. Two different directions in the ab-plane were chosen as axes of rotation. Rotating the field around [1,1,0] shifts the onset of the transition up to 3 kOe. Rotating the field around [1,0,0] stabilizes the hexagonal Aux line lattice up to the highest measured field of 30 kOe. The difference between the two axes is also reflected in the Aux line lattice distortion. (C) 1998 Elsevier Science B.V. All rights reserved.