Short-range charge order in RNiO₃ perovskites (R = Pr, Nd, Eu, Y) probed by x-ray-absorption spectroscopy

• Autores: Piamonteze, Cinthia; Tolentino, Hélio C. N.; Ramos, Aline Y.; Massa, Néstor Emilio; Alonso, José Antonio; Martínez Lope, María Jesús; Casais, Maria T.
• Año de publicación: 2005
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Exactas; Química; perovskites; spectroscopy; orthorhombic compounds; phonon-assisted conduction mechanism; unusual antiferromagnetism
• Institución: Universidad Nacional de La Plata

The short-range organization around Ni atoms in orthorhombic RNiO₃ (R = Pr, Nd, Eu) perovskites has been studied over a wide temperature range by Ni K-edge x-ray absorption spectroscopy. Our results demonstrate that two different Ni sites, with different average Ni-O bond lengths, coexist in those orthorhombic compounds and that important modifications in the Ni nearest neighbors environment take place across the metal-insulator transition. We report evidences for the existence of short-range charge-order in the insulating state, as found in the monoclinic compounds. Moreover, our results suggest that the two different Ni sites coexists even in the metallic state. The coexistence of two different Ni sites, independently on the R ion, provides a common ground to describe these compounds and shed new light in the understanding of the phonon-assisted conduction mechanism and unusual antiferromagnetism present in all RNiO₃ compounds.
Facultad de Ciencias Exactas
Centro de Química Inorgánica