2-DIMENSIONAL MEASUREMENTS OF MAGNONS

Magnon scattering in MnF2 has been recorded in a complete reciprocal p lane and not only in the main symmetry directions. This has been done effectively with the Flat-cone spectrometer E2 at the Hahn-Meitner-Ins titut using a multidetector with option of energy analysis in a large and continuous angular range. In integral measurements (without energy analysis), magnon scattering is observed with high intensity in the f orm of two butterfly wings around the magnetic Bragg reflections. The distance between the wings is a measure of the anisotropy gap energy a t the zone center. From the intensity distribution, we derived exchang e interaction parameters and the dipolar energy, in good agreement wit h the results from the triple axis measurements.