La0.67Ca0.33MnO3: defects and conducting mechanism

N.E. MASSA; H. C. N. TOLENTINO; H. SALVA; J. A. ALONSO; M. J. MARTÍNEZ-LOPE; M. T. CASAIS.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2001 vol. 233 p. 91 - 95

0304-8853

We report on temperature dependence of Mn K-edge local structure studies of La0.67Ca0.33MnO3, its relation with the behavior at the insulator?metal oxide transition (TIM), and the change of conducting regime on both sides of this phase transition in samples prepared with different protocols. Our results yield strong support for the coexistence of two non-equivalent octahedra sublattices in the insulating phase, one assigned to a localized small-polaron distorted site. Below TIM we detect one average octahedron only at temperatures in which the resistivity shows its last inflection. We also find support of this picture in our small-polaron analysis of infrared optical conductivity of the same samples