High-energy magnetic excitations in Mn₉₀Cu₁₀

The study of the magnetic excitations in Mn-rich alloys should be a good test of the multiband calculations of the spin dynamics of pure γ-Mn, which is a prototypical itinerant-electron antiferromagnet. In this paper we report the results of recent neutron inelastic scattering measurements performed on Mn₉₀Cu₁₀ at room temperature (T=0.63T_N) and up to 300 meV of energy transfer. These measurements were performed using the high-energy transfer (HET) chopper spectrometer at the ISIS spallation neutron source, Rutherford Appleton Laboratory, U.K. The results are in agreement with calculations using a model scattering function convoluted with the full HET resolution function. In this model there is a steep linear spin-wave dispersion (D≊250 meV Å) for wave vectors up to ≊1/2 of the Brillouin zone and a strong damping which is linear in the wave vector q. For larger wave vectors the spin-wave energies are constant at about 190 meV. These features are qualitatively similar to the predictions of Cade and Young for pure γ-Mn.