Abstract
The longitudinal and shear sound velocities in colossal magnetoresistive material La 0.67Ca 0.33MnO 3 sintered at 1100, 1250 and 1350 °C with average grain size 1, 3 and 5 μm, respectively, have been measured from 80 to 300 K using the pulse-echo-overlap method. A pronounced increase in the longitudinal sound velocity was observed in all samples around the insulator–metal transition temperature ( T IM∼272 K). XRD patterns showed the orthorhombic structure for all samples. The longitudinal and shear velocities showed the largest hysteresis for the sample with 3 μm grain size. A step-like shear sound velocity anomaly near 120 K during cooling or warming was observed to be dependent on the grain size.
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