ATOMIC SHORT RANGE ORDER AND SPIN DENSITY WAVE PROPAGATION IN CuMn

Abstract

Neutron scattering studies of the atomic short range order (ASRO) and spin density waves (SDW) were carried out for a Cu-35% Mn sample with an unusually high degree of ASRO that develops mostly in a single tetragonal domain. The SDW peaks show a distinctly non-cubic distribution that is readily correlated with the ASRO and which corresponds to the propagation of SDW only in the c plane of the tetragonally based ASRO. The high degree of ASRO and single domain character of this carefully heat-treated sample produces an unusually stable SDW with a higher transition temperature and a larger correlation length than is observed for quenched alloys of the same Mn content. Since SDW stability depends on structural features in the conduction electron susceptibility and on flat, parallel sections of the Fermi surface, these observations suggest that the degree of ASRO and/or the presence of single domain ASRO influences the sharpness of the relevant Fermi surface features in these alloys.