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

Abstract

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$\leq$\textit{x}$\leq$0.5), synthesized using the solid-state technique, show a change in the crystal structure from \textit{Pbnm} to \textit{R-3c} with increasing Sr substitution, attributed to the change in the tolerance factor. Prominent ferromagnetic ordering is observed in the sample with a rhombohedral structure (\textit{x}$\geq$0.3), originating from the dominant double exchange mechanism mediated by itinerant electrons. Further, the Curie temperature is smaller for the high-entropy sample with \textit{x}=0.3, as compared to La$_{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.