The equilibrium crystal structure of LnMnO3 (Ln: lanthanide) has been reported to be orthorhombic when relatively large ions from La3+ to Dy3+ are
used as Ln3+ and hexagonal when relatively small ions from Ho3+ to Lu3+ are used. It has been reported that the hexagonal phase is formed when the
tolerance factor, expressed as functions of radii of the constituent ions, is less than 0.840. In the present study, we attempted to induce oxygen deficiency
in DyMnO3 under the solidification at low oxygen partial pressure using aerodynamic levitator to reduce the tolerance factor through a decrease in the
valence of manganese ions and the accompanying increase in the ionic radius. The results showed that the oxygen deficiency increases with decreasing
oxygen partial pressure. Assuming that valence of manganese ions decreased due to the increase in oxygen deficiency, the corresponding tolerance factor
evaluated from the average ionic radii of manganese and oxygen decreased, which promoted the formation of the hexagonal phase as is the case with the
reduction of the ionic radius of Ln3+.