Effect of Fe and Cr substitution at Mn-site in structure, magnetic, magnetotesistance behaviour and dielectric properties in Pr-based manganites

The substitution of Fe or Cr at the Mn site was suggested to directly impact the interaction between Mn ions in manganites and have different effects on the compound properties which required detailed investigations. Thus, Pr₀.₇₅Na₀.₀₅K₀.2₀Mn₁̵-xFexO₃ and Pr₀.₇₅Na₀.₀₅K₀.2₀Mn₁̵-xCrxO₃ (x =0.00-0.05) manganites were prepared using solid-state synthesis to elucidate their structural, magnetic, electrical, and dielectric properties as well as magnetoresistance (MR) effect. For Pr₀.₇₅Na₀.₀₅K₀.2₀Mn₁̵-xFexO₃ series, all samples (x = 0-0.05) exhibited ferromagnetic (FM)-paramagnetic (PM) transition behaviour and a decrease of Curie temperature (TC). The reduction in TC indicates the weakening of the FM interaction involving Mn³+ and Mn⁴+ ions as Fe³+ replaces Mn³+ site. The observed large increased in resistivity with Fe substitution with the decreased in the metal-insulator transition temperature (TMI ) from 122 K (x = 0) to 80 K (x = 0.02). Under a 0.8 T applied field, all samples showed a decrease in resistivity between 30 K - 300 K, indicating the presence of MR effects. The intrinsic MR effect increase from 22% (x = 0.0) to 40% (x = 0.02) near TMI indicates Fe³+ substitution enhanced intrinsic MR effect, which may be related to the reduction of spin disordering.