NEUTRON-DIFFRACTION STUDIES OF ATOMIC AND MAGNETIC ORDER IN GAMMA-MN ALLOYS

Neutron diffraction measurements on manganese-rich alloys are presented which provide information within the areas of magnetism and metallurgy. Three aspects of the alloy behaviour are considered in the present paper in separate but related sections. In the first of these, the decomposition of the metastable gamma phase is discussed. A detailed analysis of the diffuse scattering from a gamma Mn-Ni alloy, for which the diffraction pattern shows the characteristic cusp-like peak, is made. Diffraction measurements are also presented for Mn-Pd alloys. In the second section the contributions to the diffuse scattering from gamma Mn alloys which arise from short-range order are discussed. The temperature variation of the scattering is described in relation to the well defined temperature variation of order parameters for Cu3Au. In the third section, the variation of magnetic moment with composition, for gamma Mn alloys as derived from neutron diffraction measurements at low temperature is presented.