Polarized neutron measurement of ''forbidden'' magnon scattering in Pt ₃Mn

We have employed inelastic scattering of polarized neutrons to study the nature of the magnetic response in the vicinity of the Curie temperature (T _C=493 K) for the intermetallic ferromagnet Pt₃Mn. The measurements were taken on the HB-1 triple-axis spectrometer at ORNL, with a field of 10 kOe applied along the scattering vector Q. For 0.9T_C <T<1.2T_C we observed underdamped magnons not only with the conventional (+) spin-wave polarization but also with the ''forbidden'' (-) polarization, with an intensity difference I(+)-I(-) which is approximately proportional to the magnetization. Both these observations are in agreement with the slowly fluctuating spin-density theory of itinerant ferromagnetism.