Theoretical and experimental study of octahedral tilting of Ca1−xGdxMnO3 (x = 0.05, 0.1, 0.15, 0.2) nanometric powders

• Possible Ca1−xGdxMnO3 perovskite structures were investigated by SPuDS software.
• Structure stability and alternative crystal structures were discussed.
• Orthorhombic-perovskite structure (Pnma) is the most stable form.
• Calculated data showed that MnO6 octahedra tilting increases with Gd doping.
• Infrared spectra analysis confirmed increased octahedral tilting with Gd doping.

In order to estimate theoretical stability of the perovskite structure for synthesized Ca1−xGdxMnO3 (x = 0.05, 0.1, 0.15, 0.2) nanopowders, the Goldschmidt tolerance factor Gt and global instability index GII were calculated. Furthermore, we have performed structure prediction of Ca1−xGdxMnO3 perovskites and found several possible perovskite-related phases. The influence of gadolinium amount on Mn─O bond angles and distances, tilting of MnO6 octahedra around all three axes and deformation due to the presence of the Jahn–Teller distortion around Mn3+ cation, as well as the influence of the amount of Mn3+ cation on Ca1−xGdxMnO3 compound, was examined. Ion Mn valence states were determined by bond valence calculations (BVC). Infrared active phonon modes in Ca1−xGdxMnO3 were studied by infrared reflection spectroscopy and magnetic properties were studied by using EPR (electron paramagnetic resonance) measurements.