Studies on the heusler alloys—III. The antiferro-magnetic phase in the Cu-Mn-Sb system

Abstract

A micrographic study of some alloys of the Cu-Mn-Sb system in both the as-cast and heat-treated conditions, revealed the presence of a single phase alloy (lattice parameter, a = 6·088 ± 0·003 A ̊ ) at the composition CuMnSb. Alloys having slightly less copper than the stoichiometric alloy also consisted of a single phase, although quenching was usually necessary to prevent the appearance of a second phase. Alloys with higher copper concentrations, including the alloy of composition Cu 2MnSb, contained an α-Cu solid solution, as well as the intermediate phase. X-ray and neutron diffraction investigations of CuMnSb showed the alloy to have an ordered MgAgAs (Cl b ) type structure with Cu atoms at 0, 0, 0; Mn atoms at 1 4 , 1 4 , 1 4 ; and Sb Atoms at 3 4 , 3 4 , 3 4 Antiferromagnetic reflections appeared in neutron diffraction scans at 4.2°K and were indexed using a magnetic unit cell with twice the edge lengths of the chemical unit cell. The magnetic moments of the manganese atoms were found to be oriented perpendicular to the ferromagnetic (111) planes and parallel to the [111] direction of the rhombohedral magnetic cell. The average magnetic moment per manganese site was determined to be 3·9 ± 0·1 μ B .