Produção Nacional
Anelastic spectroscopy study of the metal-insulator transition of Nd 1 − x Eu x NiO <…
2011; American Physical Society; Volume: 84; Issue: 12 Linguagem: Inglês
10.1103/physrevb.84.125127
ISSN1550-235X
AutoresF. Cordero, F. Trequattrini, Vagner Bernal Barbeta, R. F. Jardim, M. S. Torikachvili,
Tópico(s)Multiferroics and related materials
ResumoMeasurements are presented of the complex dynamic Young's modulus of NdNiO${}_{3}$ and Nd${}_{0.65}$Eu${}_{0.35}$NiO${}_{3}$ through the metal-insulator transition (MIT). Upon cooling, the modulus presents a narrow dip at the MIT followed by an abrupt stiffening of $\ensuremath{\sim}$$6%$. The anomaly is reproducible between cooling and heating in Nd${}_{0.65}$Eu${}_{0.35}$NiO${}_{3}$ but appears only as a slow stiffening during cooling in undoped NdNiO${}_{3}$, in conformance with the fact that the MIT in $R$NiO${}_{3}$ changes from strongly first order to second order when the mean $R$ size is decreased. The elastic anomaly seems not to be associated with the antiferromagnetic transition, which is distinct from the MIT in Nd${}_{0.65}$Eu${}_{0.35}$NiO${}_{3}$ . It is concluded that the steplike stiffening is due to the disappearance or freezing of dynamic Jahn-Teller (JT) distortions through the MIT, where the JT active Ni${}^{3+}$ is disproportionated into alternating Ni${}^{3+\ensuremath{\delta}}$ and Ni${}^{3\ensuremath{-}\ensuremath{\delta}}$. The fluctuating octahedral JT distortion necessary to justify the observed jump in the elastic modulus is estimated as $\ensuremath{\sim}$$3%$ but does not have a role in determining the MIT, since the otherwise-expected precursor softening is not observed.
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