Ultrasonic velocity studies in the vicinity of T(C) of bismuth doped manganites

Materials with the compositional formula La(0.67-x)Bi(x)Sr(0.33)MnO(3) (where x = 0, 0.1, 0.2, 0.3) prepared by a citrate gel route were used with a view to investigating the elastic behaviour of manganites in the vicinity of their T(C). The structural characterization of the materials clearly indicates that all the samples have a rhombohedral structure with [Formula: see text] space group. The magnetic (T(C)) as well as the metal-insulator (T(P)) transition temperatures determined by AC susceptibility and resistivity measurements, respectively, are found to decrease continuously with increasing bismuth concentration. Finally, the ultrasonic longitudinal velocities of all the samples are found to exhibit considerable softening in the vicinity of their magnetic transition temperatures, and an effort has been made to explain the observed behaviour by mean field theory and the Jahn-Teller phenomenon.