Spin waves in FeAlSi system

Results of the neutron measurements of magnon dispersion relation in Fe_2.937Al_0.381Si_0.682 (Sendust) alloy are presented. The iron-iron interaction in the FeAlSi system is considered and it is shown that the values of nearest-neighbour exchange integrals in the ordered alloys are linearly dependent on the interatomic distance, the rate of the decrease being about 40 meV/Å. This strongly supports a model of competing ferro- and antiferromagnetic interactions usually assumed for concentrated Fe-Al alloys exhibiting spin-glass behaviour.