INELASTIC NEUTRON-SCATTERING IN SOME GAMMA-MN ALLOYS BELOW AND ABOVE T-N

Inelastic neutron scattering (INS) in the FCC Mn(37% Fe, 3% Cu) alloy and in the FCT (c < a) Mn(12% Ge) and Mn(13.7% Ni) alloys was measured in a wide temperature range starting from few kelvins up to 1.3T(N). The low-temperature data are well explained in terms of neutron scatte ring on damped spin waves but essential changes start to appear alread y ca. 100-200 K below T-N. The measurements in Mn(13.7% Ni) sample wit h unequal domain population allowed one to demonstrate the appearance of neutron scattering around the magnetic BZ boundary point, equivalen t to the magnetic Brillouin zone center (MBZC) for differently oriente d domains, in addition to the ''normal'' INS around the MBZC. The inte nsity distribution around this unfulfilled MBZC is identical with the distribution around the fulfilled MBZC at T-N and above it, but differ s below T-N. (C) 1998 Elsevier Science B.V. All rights reserved.