Influence of dopant concentration on the structure and physical properties of Nd${}_{1-x}$Pb${}_x$MnO${}_3$ single crystals

Abstract

The structure of Nd${}_{1-x}$Pb${}_x$MnO${}_3$ crystals is determined by single crystal X-ray diffraction. Substitution of Pb at the Nd site results in structural phase change from tetragonal (x = 0.25) to cubic (x = 0.37). These changes are attributed to the progressive removal of inter-octahedral tilting and minimization of the octahedral distortion leading to a higher symmetry as doping concentration increases. While the unit cell volume of tetragonal structure ($P4/mmm$) is comparable to that of parent NdMnO${}_3$, the volume of cubic unit cell ($Pm\bar{3}m$) is doubled. Electron diffraction patterns support these results and rule out the possibility of twinning. Changes in transport properties as a function of temperature at different doping levels are in accordance with the observed structural changes. It is noticed that $T_c$ and $T_{MI}$ increase with x.

8 figures, Communicated to Journal of Materials Chemistry