Evolution of Ni Local Structure in NdNiO3 Perovskite Across the Metal-InsulatorTransition

C. PIAMONTEZE; HELIO C. N. TOLENTINO; A. Y. RAMOS; N. E. MASSA.; J. A. ALONSO,; M. J. MART´ıNEZ-LOPES; M.T. CASAIS

PHYSICA SCRIPTA - (Print)

IOP PUBLISHING LTD

Lugar: Londres; Año: 2005 vol. T115 p. 648 - 650

0031-8949

NdNiO3 presents a metal-insulator (MI) transition at 200K with decreasing temperature. This system was characterized by neutron diffraction as orthorhombic with a very symmetric Ni site and almost no modification at the NiO6 octahedra is observed across the transition.We carried out EXAFS measurements on NdNiO3 from room temperature down to 10 K, crossing the MI transition and observed important local modifications at the Ni site. The phase derivative method shows that there are distorted Ni sites, with at least two different Ni-O distances, along all the temperature range measured. The modification across the MI transition concerns the increasing of the distorted phase. This hypothesis is sustained by the behavior of the Debye-Waller factor (2) with temperature. With decreasing temperature, when the sample is around TMI 2 rapidly increases due to thegrowing amount of distorted sites. These results give basis for a discussion in terms of a percolative transition.