The spatial distribution of magnetisation density in Mn5Ge3

Abstract

The spatial distribution of magnetisation density in the intermetallic compound Mn5Ge3 has been determined from a polarised neutron diffraction single-crystal study at 4.2 K. The positional and thermal parameters of the structure were derived from an unpolarised neutron study at 60 K, which also served to characterise the extinction in the material. The observed magnetic structure factors were fitted by a multipole expansion based on free-atom form factors for each of the two crystallographically inequivalent manganese atoms in the unit cell. The magnetic moment of the Mn1 atom with site symmetry 32 is 1.96(3) mu B and that of Mn2 with site symmetry mm is 3.23(2) mu B. The radial form factor of the Mn1 atom is found to be significantly contracted relative to that of a free Mn2+ ion. Evidence is presented that Mn-Mn interactions are the major factor leading to the difference in the moments on the two sites.