Sr2MgHfFeO6 crystallizes in the monoclinic C2/m space group. Sr(1) is bonded in a 9-coordinate geometry to one Mg(1), four equivalent O(1), and four equivalent O(2) atoms. Mg(1) is bonded in a square co-planar geometry to two equivalent Sr(1) and four equivalent O(2) atoms. Hf(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form HfO6 octahedra that share corners with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. Fe(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form FeO6 octahedra that share corners with six equivalent Hf(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to four equivalent Sr(1), one Hf(1), and one Fe(1) atom. In the second O site, O(2) is bonded to two equivalent Sr(1), one Mg(1), one Hf(1), and one Fe(1) atom to form a mixture of distorted corner, edge, and face-sharing OSr2HfMgFe trigonal bipyramids.
Sr2MgHfFeO6 crystallizes in the monoclinic C2/m space group. Sr(1) is bonded in a 9-coordinate geometry to one Mg(1), four equivalent O(1), and four equivalent O(2) atoms. The Sr(1)-Mg(1) bond length is 3.03 Å. There are a spread of Sr(1)-O(1) bond distances ranging from 2.92-3.03 Å. There are two shorter (2.70 Å) and two longer (2.71 Å) Sr(1)-O(2) bond lengths. Mg(1) is bonded in a square co-planar geometry to two equivalent Sr(1) and four equivalent O(2) atoms. All Mg(1)-O(2) bond lengths are 2.01 Å. Hf(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form HfO6 octahedra that share corners with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. Both Hf(1)-O(1) bond lengths are 2.14 Å. All Hf(1)-O(2) bond lengths are 2.05 Å. Fe(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form FeO6 octahedra that share corners with six equivalent Hf(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. Both Fe(1)-O(1) bond lengths are 2.63 Å. All Fe(1)-O(2) bond lengths are 2.03 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to four equivalent Sr(1), one Hf(1), and one Fe(1) atom. In the second O site, O(2) is bonded to two equivalent Sr(1), one Mg(1), one Hf(1), and one Fe(1) atom to form a mixture of distorted corner, edge, and face-sharing OSr2HfMgFe trigonal bipyramids.