FERRIMAGNETIC STRUCTURE OF MN2C02C

The carbide Mn2Co2C has been found to be ferrimagnetic with a Neel temperature of 535°C by means of neutron diffraction. It has a cubic unit cell with an Mn atom at the cube corner and the Carbon atom at the body centre. The face centre sites are taken up by the other Mn and the two Co atoms in a statistical manner. The Mn moments are aligned anti-parallel to each other while the two Co moments are parallel to the comer Mn moment. The most reasonable values for the moments are: 4.0 μB for the corner Mn atom, 3.36 μB for the face centre Mn and 1.25 μB for each Co atom. The smaller moments of the face centre atoms arise from the influence of the carbon atom. Polarised neutrons were used to choose a structure having cubic symmetry over one of tetragonal symmetry. © 1969.