Ultrasonic studies on colossal magnetoresistive Nd0.67A0.33MnO3 (A = Ca, Sr)

The colossal magnetoresistive material Nd0.67A0.33MnO3 (A = Ca, Sr) has been investigated through sound velocity measurements using pulse-transmission method at 1 MHz. Significant hardening of longitudinal velocity below Curie temperature (TC) has been observed, which is attributed to significant decrease of the static Jahn-Teller distortion of the MnO6 octahedra due to spin–lattice coupling in this material. The elastic moduli at room temperature have been determined and porosity corrections have been reported. The compositional dependence of elastic moduli is interpreted in terms strength of interatomic bonding, which a consequence of A-site ionic radius 〈rA〉.