Charge transport and ultrasonic properties in La0.57Ca0.43MnO3 perovskite

The resistivity, ac susceptibility, ultrasonic sound velocity and attenuation have been measured in the single-phase La0.57Ca0.43MnO3 bulk sample. Sharp attenuation peaks and dramatic stiffening in sound velocities for both longitudinal and transverse waves were observed near the paramagnetic to ferromagnetic phase transition temperature, TC, implying a strong Jahn–Teller effect. The ultrasonic anomalies near TC are interpreted in terms of a significant reduction of the Jahn–Teller distortion of the Mn3+O6 octahedra, resulting from the coupling of the ferromagnetic spin ordering to the crystal lattice (i.e. spin–lattice coupling) below TC. The resistivity undergoes a broad insulator–metal transition far below TC. This phenomenon is related to a sufficiently strong electron–lattice coupling in the ferromagnetic state.