Effect of Ti(4+) substitution on structural, transport and magnetic properties of La(0.67)Sr(0.33)Mn(1-x)Ti(x)O(3)

Abstract

La(0.67)Sr(0.33)Mn(1-x)Ti(x)O(3) (0 less than or equal to x less than or equal to 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 less than 0.10 show metal-insulator transition and those with x greater than or equal to 0.10 exhibit insulating behavior over the entire temperature range investigated. A gradual transition occurs from the ferromagnetic-metallic state to the ferromagnetic-insulator state with increasing Ti substitution. Lattice parameters and bond lengths of Mn and its near neighbors 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.