Correlation Between Charge, Spin and Lattice in La-Eu-Sr Manganites

To understand the structural, electrical, magnetic, elastic and anelastic properties of La0.67-x Eu (x) Sr0.33MnO3 (0.30a parts per thousand currency signxa parts per thousand currency sign0.39) manganites, a series of samples was prepared by citrate gel route. X-ray diffraction studies along with Rietveld analysis indicate the samples crystallize in single phase with Pnma space group. Studies on the variations of magnetization with temperature indicate that the Curie transition temperature (T (C)) decreases with increasing Eu content. Furthermore, Eu substitution is found to increase the electrical resistivity and significantly enhances the colossal magnetoresistance effect, while it is found to decrease the characteristic metal-insulator transition temperature (T (P)). On analyzing the electrical resistivity data, it has been concluded that the resistivity below T (P) can be explained based on electron-electron, electron-phonon and two magnon scattering processes, while that above T (P), the adiabatic small polaron model is found to explain the observed behavior. Finally, the longitudinal modulus (L) and internal friction (Q (-1)) have been measured and a dramatic change in L (T) is observed at T (C), accompanied by a sharp peak in Q (-1) (T). Simultaneous occurrence of magnetic, transport and lattice anomalous behavior at T (C) indicate the presence of strong electron-phonon and spin-phonon interactions in these manganites.