Lattice effects in manganites

Abstract

Dedicated to Professor Jozef T. Devreese on the occasion of his 65th birthday PACS 63.20.KrThe interplay of the electron-phonon interaction and of the double and super-exchange magnetic effects in the La 1Àx Ca x MnO 3 perovskites with 0 < x < 0:5 is studied. It is shown that treating the electronphonon interaction in a fully quantum manner in the intermediate electron-phonon coupling regime a charge density instability occurs near the metal-insulator transition, induced by either temperature or hole doping. Also the effects of the magnetic field and the oxygen isotope substitution on the phase diagram, the electron-phonon correlation function and the infrared absorption at x ¼ 0:3 is studied. The lattice displacements show a strong correlation with the conductivity and the magnetic properties of the system. Finally the conductivity spectra are characterized by a marked sensitivity to the external parameters near the phase boundary.

Intrinsic and extrinsic inhomogeneities in mixed-valence manganites

“…Some other examples of the phaseseparation models can be found in Refs. [4,7,8,9,10] (actually, there is a vast literature on the subject, but it can not be cited more fully in this short communication). On the basis of this, it is hoped to explain transport and magnetoresistive properties (including CMR) of manganites taking into account the phase separation effects.…”