Ultrasonic anomalies in La1/3Sr2/3MO3 (M=Fe, Mn) -: art. no. 041920

The longitudinal ultrasonic velocity (V-l), magnetization, specific heat, and resistivity of polycrystalline La1/3Sr2/3FeO3 have been measured between 20 and 300 K. The material undergoes charge-ordering (CO) transition at about 200 K accompanied by an antiferromagnetic ordering. Upon cooling down from 300 K, a substantial softening in V-l above the charge-ordering transition temperature T-CO and dramatic stiffening below T-CO are observed. This feature is similar in character to that of charge-ordered La1/3Sr2/3MnO3, and gives clear evidence for electron-phonon coupling in La1/3Sr2/3FeO3. Below 181 K, another unexpected softening in V-l is observed, which is attributed to the breathing-type distortion of an Fe-O octahedron. (c) 2006 American Institute of Physics.