Verification of the de Wolff hypothesis concerning the symmetry of β-MnO2

The symmetry lowering from tetragonal to orthorhombic is demonstrated using high-resolution diffraction and also justified by using the magnetic superspace groups formalism for the rutile-type compound β-MnO2. The (lower) orthorhombic symmetry is observed at temperatures both below and above the Néel temperature. The magnetic ordering of β-MnO2is of spin density type and not screw-type helical. The results support the de Wolff [Acta Cryst.(1959),12, 341–345] hypothesis about the orthorhombic symmetry of β-MnO2.