抄録
The antiferromagnetism of disordered γ-FeMn alloys has been studied by neutron diffraction and Mössbauer effect. The average magnetic moment per atom at 0°K decreases with decreasing Fe concentration from 1.94μB for 69.1 at% Fe to 1.08μB for 47 at% Fe. The hyperfine field at 0°K acting on the Fe nucleus, however, remains almost constant at about 40 kOe±3 kOe for this concentration range. The temperature dependence of the sublattice moment for 69.1 at% Fe fits with the Brillouin function BJ(x) with J=1. The decrease of the moment near the Néel temperature becomes steeper when the concentration of Fe is lower. In contrast with it, the temperature dependence of the hyperfine field is independent of concentration, and is markedly different from the temperature dependence of the sublattice moment for any concentration. The results indicate that the magnetic moments on Fe and Mn atoms behave with temperature in fairly different ways in this alloy system. The magnetic form factor of γ-FeMn alloys was also determined.
