Magnetic Structure ofMn4N-Type Compounds

Abstract

A series of ${\mathrm{Mn}}_4$N-type compounds has been investigated by means of magnetic saturation measurements and neutron diffraction experiments. Reinvestigation of ${\mathrm{Mn}}_4$N has given revised moments with $3.85{\mu }_B$ at the corner of the cubic unit cell antiparallel to the three face-centered moments of $0.90{\mu }_B$ at 77°K. Replacement of the nitrogen, located at the body-centered position, by carbon lowers the saturation moment by increasing the moment of the face-centered Mn while leaving the corner atom unchanged. Partial replacement of the nitrogen by vacancies also decreases the saturation moment. Small vacancy concentrations increase the face-centered moments while leaving the corner moment essentially unchanged. At larger vacancy concentrations, both the corner and face-centered moments decrease. These results are explicable in terms of a model in which nitrogen acts as an electron donor and the various local environments cause differing energy level splittings of the Mn atoms.