Ultrasonic study of phase separation in La1-xSrxMnO3(x ≈ 0.125)

The temperature dependences of longitudinal velocities and attenuations of La1-xSrxMnO3(x approximate to 0.125) single phase polycrystal were measured. An ultrasonic velocity softening accompanied by a sharp peak in attenuation was found near the Curie temperature (T-C) of paramagnetic insulator phase to ferromagnetic metal phase. Analysis indicates that the ultrasonic anomalies near T-C are due to the spin-phonon interaction. The coexistence of the ferromagnetic metal regions, ferromagnetic insulator regions and antiferromagnetic insulator regions in La0.875Sr0.125MnO3 were observed below 200 K by resistance and ac susceptibility measurements. Simultaneously, a dramatic softening in ultrasonic velocity accompanied by a wide peak in attenuation showing an obvious hysteresis was found. This suggested that the transition accompanied by phase separation is of the first order transition associated with the Jahn-Teller distortion. It also proved that the ultrasonic method is particularly useful for phase separation investigation.