Sound velocity in perovskite manganites La0.67Ca0.33MnO3 with different grain sizes

Abstract

The longitudinal and shear sound velocities in colossal magnetoresistive material La0.67Ca0.33MnO3 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 (TIM∼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. © 2007 Elsevier B.V. All rights reserved.