Magnetic and Electrical Properties of high-entropy rare-earth manganites

Detailed investigations of structural, magnetic and electronic transport properties of hole-doped high-entropy rare-earth manganites are presented. The high-entropy samples (LaNdPrSmEu)${}_{1-x}$Sr${}_x$MnO${}_3$ (0$\le$$\mathit{\text{x}}$$\le$0.5), synthesized using the solid-state technique, show a change in the crystal structure from $\mathit{\text{Pbnm}}$ to $\mathit{\text{R-3c}}$ with increasing Sr substitution, attributed to the change in the tolerance factor. Prominent ferromagnetic ordering is observed in the sample with a rhombohedral structure ($\mathit{\text{x}}$$\ge$0.3), originating from the dominant double exchange mechanism mediated by itinerant electrons. Further, the Curie temperature is smaller for the high-entropy sample with $\mathit{\text{x}}$=0.3, as compared to La${}_{0.7}$Sr${}_{0.3}$MnO${}_3$, suggesting a strong relation between the Curie temperature and the Mn-O-Mn bond angle associated with the reduced ionic radii at the rare-earth site. The electrical resistivity of the high-entropy samples is larger than those of La${}_{1-x}$Sr${}_x$MnO${}_3$, which can be ascribed to the reduced bandwidth due to the enhanced structural distortion. A concomitant rise in magnetoresistance is observed for high-entropy samples with the increase in Sr concentration. These findings considering the configurational complexity of different rare-earths advance the understanding of high-entropy rare earth manganites.