Elastic Properties of Colossal Magnetoresistive Manganites $R_{0.67} Sr_{0.33} Mn O_3$ (R = Pr, Nd, Gd)

The polycrystalline bulk samples of $R_{0.67} Sr_{0.33} Mn O_3$ (R = Pr, Nd, Gd) were prepared by solid state reaction method and characterized by powder X-ray diffraction. The room temperature elastic behavior of these materials was investigated by employing ultrasonic pulse transmission technique at 1 MHz. The values of elastic constants were computed from longitudinal and shear velocities. The measured values were corrected to zero porosity using Hasselman and Fulrath's formulae. The variation of elastic moduli with the size of rare earth ion is interpreted in terms of strength of interatomic bonding.