Synthesis and characterization of (Nd1-xSmx)CrO3: compositional influence on structural, vibrational, magnetic and optical properties

The (Nd 1- x Sm x )CrO 3 (0 ≤ x ≤ 1) solid solution was synthesized by conventional solid-state reactions. X-ray powder diffraction data Rietveld refinements confirm that each compound could be described in the orthorhombic space group Pnma . Successive replacement of Nd 3+ by smaller Sm 3+ cations induces an anisotropic lattice response, characterized by contraction of the b- and c- lattice parameters with a slight expansion in the a - direction, resulting in an overall linear decrease of the unit cell volume. Structure analysis reveals that lattice accommodation occurs predominantly through octahedral tilting and oxygen displacement rather than a significant compression of the Cr-O bond. This effect is evidenced by the nearly invariant CrO 6 octahedral volume and quadratic elongation across the solid solution. The CrO 6 octahedra exhibit higher tilting for the Sm-rich compositions, highlighting how the perovskite-type A -site substitution reduces the tolerance factor. Temperature-dependent magnetization reveals long-range antiferromagnetic ordering of the Cr 3+ sublattice. The magnetic response of the intermediate compositions (0 < x < 1) exhibits two distinct anomalies near the closely spaced Néel temperatures of the endmembers. The negative Weiss temperatures obtained from the paramagnetic regime further support the dominant antiferromagnetic interactions. The absolute values of the Curie–Weiss temperatures increase with increasing Sm content, consistent with systematic changes in the Cr–O–Cr superexchange pathway caused by enhanced octahedral tilting. The spin reorientation transition observed for the Nd-rich compositions is gradually suppressed with increasing Sm substitution. In the same way, Raman as well as FTIR spectroscopic data demonstrate systematic hardening of the optical modes, consistent with the lattice contraction (quasi-harmonic). UV/Vis diffuse reflectance data reveal that the optical band gap remains almost constant irrespective of the chemical composition.