Ultrasonic study on the Jahn-Teller effect near different phase transitions in La1/3Sr2/3MO3 (M=Mn, Fe, Co)

► Different ultrasonic anomalies are observed near different phase transitions in La1/3Sr2/3MO3. ► For M=Mn, this anomaly is due to the Jahn-Teller effect of Mn3+. ► For M=Fe, the instability of Fe4+ results to the complex ultrasonic anomalies. ► For M=Co, the intermediate spin Co3+ leads to the anomaly in the ferromagnetic metal state.