MgCoMnO4 crystallizes in the monoclinic Pm space group. Mg(1) is bonded in a distorted rectangular see-saw-like geometry to one O(2), one O(3), and two equivalent O(4) atoms. Mn(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form MnO6 octahedra that share edges with two equivalent Mn(1)O6 octahedra and edges with four equivalent Co(1)O6 octahedra. Co(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form CoO6 octahedra that share edges with two equivalent Co(1)O6 octahedra and edges with four equivalent Mn(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Mn(1) and one Co(1) atom. In the second O site, O(2) is bonded to one Mg(1), one Mn(1), and two equivalent Co(1) atoms to form distorted OMgMnCo2 tetrahedra that share corners with two equivalent O(2)MgMnCo2 tetrahedra, corners with two equivalent O(4)Mg2Mn2Co trigonal bipyramids, corners with four equivalent O(3)MgMnCo2 trigonal pyramids, edges with two equivalent O(4)Mg2Mn2Co trigonal bipyramids, and  an edgeedge with one O(3)MgMnCo2 trigonal pyramid. In the third O site, O(3) is bonded to one Mg(1), one Mn(1), and two equivalent Co(1) atoms to form OMgMnCo2 trigonal pyramids that share corners with four equivalent O(2)MgMnCo2 tetrahedra, corners with two equivalent O(4)Mg2Mn2Co trigonal bipyramids, corners with two equivalent O(3)MgMnCo2 trigonal pyramids,  an edgeedge with one O(2)MgMnCo2 tetrahedra, and edges with two equivalent O(4)Mg2Mn2Co trigonal bipyramids. In the fourth O site, O(4) is bonded to two equivalent Mg(1), two equivalent Mn(1), and one Co(1) atom to form distorted OMg2Mn2Co trigonal bipyramids that share corners with two equivalent O(2)MgMnCo2 tetrahedra, corners with two equivalent O(3)MgMnCo2 trigonal pyramids, edges with two equivalent O(2)MgMnCo2 tetrahedra, edges with two equivalent O(4)Mg2Mn2Co trigonal bipyramids, and edges with two equivalent O(3)MgMnCo2 trigonal pyramids.
MgCoMnO4 crystallizes in the monoclinic Pm space group. Mg(1) is bonded in a distorted rectangular see-saw-like geometry to one O(2), one O(3), and two equivalent O(4) atoms. The Mg(1)-O(2) bond length is 1.91 Å. The Mg(1)-O(3) bond length is 2.00 Å. Both Mg(1)-O(4) bond lengths are 2.08 Å. Mn(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form MnO6 octahedra that share edges with two equivalent Mn(1)O6 octahedra and edges with four equivalent Co(1)O6 octahedra. The Mn(1)-O(2) bond length is 1.91 Å. The Mn(1)-O(3) bond length is 1.93 Å. Both Mn(1)-O(1) bond lengths are 1.90 Å. Both Mn(1)-O(4) bond lengths are 2.11 Å. Co(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form CoO6 octahedra that share edges with two equivalent Co(1)O6 octahedra and edges with four equivalent Mn(1)O6 octahedra. The Co(1)-O(1) bond length is 2.27 Å. The Co(1)-O(4) bond length is 2.21 Å. Both Co(1)-O(2) bond lengths are 2.10 Å. Both Co(1)-O(3) bond lengths are 2.03 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Mn(1) and one Co(1) atom. In the second O site, O(2) is bonded to one Mg(1), one Mn(1), and two equivalent Co(1) atoms to form distorted OMgMnCo2 tetrahedra that share corners with two equivalent O(2)MgMnCo2 tetrahedra, corners with two equivalent O(4)Mg2Mn2Co trigonal bipyramids, corners with four equivalent O(3)MgMnCo2 trigonal pyramids, edges with two equivalent O(4)Mg2Mn2Co trigonal bipyramids, and  an edgeedge with one O(3)MgMnCo2 trigonal pyramid. In the third O site, O(3) is bonded to one Mg(1), one Mn(1), and two equivalent Co(1) atoms to form OMgMnCo2 trigonal pyramids that share corners with four equivalent O(2)MgMnCo2 tetrahedra, corners with two equivalent O(4)Mg2Mn2Co trigonal bipyramids, corners with two equivalent O(3)MgMnCo2 trigonal pyramids,  an edgeedge with one O(2)MgMnCo2 tetrahedra, and edges with two equivalent O(4)Mg2Mn2Co trigonal bipyramids. In the fourth O site, O(4) is bonded to two equivalent Mg(1), two equivalent Mn(1), and one Co(1) atom to form distorted OMg2Mn2Co trigonal bipyramids that share corners with two equivalent O(2)MgMnCo2 tetrahedra, corners with two equivalent O(3)MgMnCo2 trigonal pyramids, edges with two equivalent O(2)MgMnCo2 tetrahedra, edges with two equivalent O(4)Mg2Mn2Co trigonal bipyramids, and edges with two equivalent O(3)MgMnCo2 trigonal pyramids.