  The paper reports theoretical evidence that the multi-spin-axis magnetic
structure proposed in 1964 by van Laar actually does exist in CoO. This
tetragonal spin arrangement produces both the strong tetragonal and the weaker
monoclinic distortion experimentally observed in this material. The monoclinic
distortion is proposed to be a "monoclinic-like" distortion of the array of the
oxygen atoms, comparable with the rhombohedral-like distortion of the oxygen
atoms recently proposed to be present in NiO and MnO. The monoclinic-like
distortion has no influence on the tetragonal magnetic structure which is
generated by a special nonadiabatic atomic-like motion of the electrons near
the Fermi level. It is argued that it is this special atomic-like motion which
qualifies CoO to be a Mott insulator.
