Magnetic Structure of α-Mn

A neutron diffraction study has been made on single crystal specimens of α-Mn at 4.4°K, 60°K, and several other temperatures. Five types of magnetic form factor were in turn employed in the analysis. The magnetic structure is described by a single non-collinear configuration throughout the temperature range below T N with relatively large magnetic moments in Sites I, II and small moments in Sites III, IV, irrespective of which form factor is chosen. The experimental results seem to favor a localized moment model rather than a spin density wave model. When the analysis is based on the localized moment model, moments of 1.9, 1.7, 0.6 and 0.2 5 µ B may be assigned to Site I, II, III, and IV, respectively at 4.4°K, and the spin density in the atom is a superposition of a positive 3d-density and a negative 4s-density. The dependence of the effective exchange interaction coefficient on the inter-atomic distance is discussed.