Temperature dependent structural properties of Mn_1.90M_0.10O₃ (M = Cr and Fe)

The polycrystalline samples of Mn_1.90Cr_0.10O₃ (MCO) and Mn_1.90Fe_0.10O₃ (MFO) have been investigated for their temperature dependent magnetic and structural properties. The Cr and Fe substitutions have significant effect on the magnetic and structural properties of Mn₂O₃. Like pristine Mn₂O₃, the Cr and Fe substituted samples MCO and MFO also exhibit two antiferromagnetic transitions; one at ∼77 K, ∼80 K, respectively and another at ∼40 K. Our room temperature synchrotron x-ray powder diffraction (SXRD) results confirm that both the MCO and MFO samples crystallize in cubic symmetry. The temperature dependent SXRD results demonstrate the cubic to orthorhombic structural transition for the studied samples. The pristine Mn₂O₃ shows cubic to orthorhombic transition around 310 K, whereas this structural transition shifted towards lower temperature side with these substitutions i.e. around 240 K for MCO and 260 K for MFO. Interestingly, the centrosymmetric Pcab to non-centrosymmetric Pca2₁ change in symmetry is also resolved at the ferroelectric ordering temperature for MCO.