Abstract
? 2022 Elsevier B.V.We report the synthesis, structural, magnetic, electrical transport, magnetoelectric and thermoelectric properties of ″112″-layered double perovskite Y1?xLnxCo2O5.5 (Ln = Sm, Eu and Gd; x = 0, 0.5 and 1) cobaltites. YBaCo2O5.50 exhibits simultaneous structural, magnetic and electrical transitions around 300 K. Whereas LnBaCo2O5.50 (Ln = Sm, Eu and Gd) exhibit well separated TC and TIM, respectively, below and above 300 K. It is expected from the chemical viewpoint that the substitution of Ln by Y in LnBaCo2O5.50 should result in proximity of TC and TIM. However, our investigation demonstrates that though TC shows significant upward shift, TIM exhibits robustness. This suggests that the electrical and magnetic transitions are decoupled. The large MR [(ρH-ρ0)/ρ0] values (~50%) at low temperatures are observed for Eu and Gd-phases. The low temperature electrical conduction mechanism is of variable range hopping (VRH) type and the thermoelectric properties suggest the p-type polaronic conductivity or hole like carriers in the samples. The observed results can be understood in the framework of electronic phase separation and the metal-insulator transition from viewpoint of structural transition instead of the spin state transition.
NSTL
Elsevier