Elastic anomalies of La 0.67Sr 0.33− xBa xMnO 3 in the vicinity of TC

Abstract

With a view to understand the elastic behaviour of a material system, La 0.67Sr 0.33− x Ba x MnO 3 (where x=0, 0.1, 0.2, and 0.33) especially in the vicinity of their magnetic transition temperature T C , a systematic investigation of ultrasonic velocity over a temperature range 300–400 K has been carried out. The materials prepared by citrate gel route, were characterized structurally by XRD and on analyzing the XRD patterns, it has been concluded that all the samples are having rhombohedral structure with space group of R3̄c. The magnetic ( T C ) transition temperatures determined by AC susceptibility measurements are found to decrease continuously with increasing barium concentration. Finally, the ultrasonic longitudinal velocities of all the samples are found to exhibit considerable softening in the vicinity of their magnetic transition temperatures, T C and the observed behaviour is explained using mean field theory and Jahn–Teller theorem.