Produção Nacional
Revisado por pares
Metal–insulator transition in Nd 1− x Eu x NiO 3 compounds
2006; IOP Publishing; Volume: 18; Issue: 26 Linguagem: Inglês
10.1088/0953-8984/18/26/030
ISSN1361-648X
AutoresM. T. Escote, Vagner Bernal Barbeta, R. F. Jardim, Javier Campo,
Tópico(s)Multiferroics and related materials
ResumoPolycrystalline Nd 1-x EuxNiO 3 (0 ≤ x ≤ 0.5) compounds were synthesized in order to investigate the character of the metal-insulator (MI) phase transition in this series.Samples were prepared through the sol-gel route and subjected to heat treatments at ∼1000 • C under oxygen pressures as high as 80 bar.X-ray Diffraction (XRD) and Neutron Powder Diffraction (NPD), electrical resistivity ρ(T ), and Magnetization M (T ) measurements were performed on these compounds.The results of NPD and XRD indicated that the samples crystallize in an orthorhombic distorted perovskite structure, space group P bnm.The analysis of the structural parameters revealed a sudden and small expansion of ∼0.2% of the unit cell volume when electronic localization occurs.This expansion was attributed to a small increase of ∼0.003 Å of the average Ni-O distance and a simultaneous decrease of ∼-0.5 • of the Ni-O-Ni superexchange angle.The ρ(T ) measurements revealed a MI transition occurring at temperatures ranging from T MI ∼ 193 to 336 K for samples with x = 0 and 0.50, respectively.These measurements also show a large thermal hysteresis in NdNiO 3 during heating and cooling processes suggesting a first-order character of the phase transition at T MI .The width of this thermal hysteresis was found to decrease appreciably for the sample Nd 0.7 Eu 0.3 NiO 3 .The results indicate that cation disorder associated with increasing substitution of Nd by Eu is responsible for changing the first order character of the transition in NdNiO 3 .
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