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 1C with average grain size 1, 3 and 5 mm, respectively, have been measured from 80 to 300K 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 (TIM272 K). XRD patterns showed the orthorhombic structure for all samples. The longitudinal and shear velocities showed the largest hysteresis for the sample with 3 mm grain size. A step-like shear sound velocity anomaly near 120K during cooling or warming was observed to be dependent on the grain size.

Structure, magnetic properties and Mössbauer spectra of La0.67Sr0.33FexMn1 − xO3 manganites oxide prepared by mechanical ball milling method

“…Our crystallographic parameters are almost identical and comparable to those obtained by L.S. Ewe et al [25] of La 0.67 Ca 0.33 MnO 3 sample prepared by the co-precipitation method. Figure 3 shows typical SEM images summarizing the results of the electron microscopy observations.…”

Synthesis and on-line ultrasonic characterisation of bulk and nanocrystalline La0.68Sr0.32MnO3 perovskite manganite

“…It is also evident from the above studies that T C is decreased to 370 K from 375 K, which is attributed to the decrease in grain size. It is inferred from earlier studies that the decrease in grain size leads to lowering in ferromagnetic transition temperature [43,44], as observed in the present investigation and there is no sharp FM to PM transition [45].…”

On-line phase transition in La1−xSrxMnO3(0.28 ≤ x ≤ 0.36) perovskites through ultrasonic studies

“…The U L and U S in colossal magnetoresistive material La 0.67 Ca 0.33 MnO 3 have been measured from 80 to 300 K. A pronounced increase in U L has been observed in all samples around the insulator-metal transition temperature (272 K). The observed anomaly in sound velocity at 120 K depends on the grain size [17]. The characteristic softening and the subsequent hardening in U S in La 1Àx Ca x MnO 3 (0.46 x 0.50) perovskite manganite materials have been observed below the ferromagnetic transition temperature (T c ).…”