Low-temperature structural phase transitions in rare earths substituted calcium manganese oxides [Ca_2-xLn_xMnO₄, where Ln=Nd, Sm-Lu and Y]

The structural phase transitions of Ca_2-xLn_xMnO₄ (Ln=Nd, Sm-Lu and Y) were investigated by powder X-ray diffraction in the temperature range 10-1000 K. The maximum amount of the substitution, x, for the formation of the single phase had a tendency to decrease with decreasing ionic radii of rare earths. The new type of orthorhombic phase with a distortion along [100] direction of the undistorted tetragonal phase was found for Ln=Nd, Sm, Lu and Y with x=0.2. The low temperature tetragonal phase was observed in the case of Ln=Sm with x=0.3.