Effect of Ti4+ substitution on structural, transport and magnetic properties of La0.67Sr0.33Mn1-xTixO3

Abstract

La$_{0.67}$Sr$_{0.33}$Mn$_{1-x}$Ti$_x$O$_{3}$ ($0 \le x \le 0.20$) polycrystalline materials are prepared by employing lower annealing temperature compared to the temperatures reported for the materials of the same composition. The transport and magnetic properties of these materials are significantly different from those compounds prepared at higher annealing temperature. Samples with $x < 0.10$, show metal-insulator transition and those with $x \ge 0.10$ exhibit insulating behavior over the entire temperature range investigated. A gradual transition occurs from ferromagnetic-metallic state to ferromagnetic-insulator state with increasing Ti substitution. Lattice parameters and bond lengths of Mn and its near neighbours however do not change appreciably with the dopant content $x$ in these materials. It is shown that Ti$^{4+}$ doping in the low temperature annealed samples is inhomogeneous resulting in isolated Mn rich regions that are connected by a variable range hopping polaron.