Magnetic Structure of Cobalt Manganite by Neutron Diffraction

Cobalt manganite ${\mathrm{CoMn}}_2{\mathrm{O}}_4$ is prepared at 1250°C and quenched from different temperatures. It always crystallizes in centered tetragonal system but its lattice parameters and inversion degree change by quenching. Measurements of paramagnetic susceptibility above the Curie temperature and magnetization in high fields show the ferrimagnetic behavior of ${\mathrm{CoMn}}_2{\mathrm{O}}_4$ with a very weak spontaneous magnetization at 4.2°K. Anisotropy is very strong. The magnetic structure of ${\mathrm{CoMn}}_2{\mathrm{O}}_4$ has been worked out from low‐temperature neutron‐diffraction patterns. In tetrahedral sublattice, spins are collinear, and their mean length is in very good agreement with theory assuming that Co²⁺ and Mn³⁺ moments are spin‐only ones. In octahedral sublattice, a Yafet‐Kittel structure is in very good agreement with experimental results. The $B$ resulting moment is collinear with the $A$ spins along the [110] direction. The net spin value in $B$ sublattice is much smaller than the theoretical one. This low‐temperature structure becomes collinear at 70°K.