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 cr ystalline c-axis. Previously we have reported on a square to hexagonal symmetry transition of the fluc line lattice below 1 kOe for H parall el to c. We find that the rotation of the field shifts the transition to higher fields in agreement with theoretical prediction. Two differe nt directions in the ab-plane were chosen as axes of rotation. Rotatin g 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 li ne lattice up to the highest measured field of 30 kOe. The difference between the two axes is also reflected in the Aux line lattice distort ion. (C) 1998 Elsevier Science B.V. All rights reserved.