Cr 3 + ‐Induced Structural and Magneto‐Transport Properties in Charge‐Ordered Sm 0.5 Ca 0.5 MnO 3 Manganites

Polycrystalline Sm 0.5 Ca 0.5 Mn 1‐x Cr x O 3 ( x = 0.00, 0.03, 0.05, 0.07, and 0.09) manganites were synthesized using the conventional solid‐state reaction method. The effect of Cr 3+ substitution on the structural, electrical and magnetic properties of Sm 0.5 Ca 0.5 MnO 3 was studied. Room‐temperature X‐ray diffraction combined with Rietveld refinement confirmed that all samples crystallize in the orthorhombic Pnma structure. A gradual decrease in unit‐cell volume with increasing Cr 3+ content indicates successful Cr substitution into the lattice. Electrical resistivity measurements revealed that the parent compound ( x = 0) exhibits insulating behaviour due to strong charge ordering and carrier localization. Increasing Cr 3 + substitution progressively suppresses the charge‐ordered state and promotes a metal–insulator transition. For x = 0.05, a transition occurred at 72.43 K under an applied magnetic field of 0.8 T. The emergence of a ferromagnetic‐metallic (FMM) phase is attributed to the weakening of Coulomb interactions and Jahn–Teller distortions within the Mn─O network. AC susceptibility measurements revealed a charge‐ordering transition near 270 K for x = 0, while Cr substitution ( x = 0.05–0.09) suppressed charge ordering and reduced the Curie temperature from 100.22 to 86.29 K. The enhanced FMM behaviour is associated with strengthened Mn 3 + ─O─Cr 3 + interactions and weakened antiferromagnetic interactions. Resistivity analysis further showed that charge transport is dominated by residual resistivity in the metallic region, whereas variable‐range hopping and small‐polaron hopping govern conduction in the insulating region. These findings demonstrate that Cr 3+ substitution effectively tunes the structural, electrical, and magnetic properties of Sm 0.5 Ca 0.5 MnO 3 through the suppression of charge ordering and stabilization of the FMM state.