CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Unidad Ejecutora - UE
congresos y reuniones científicas
High pressure local probe of phase transitions in RNiO3 (R= Nd, Pr)
NESTOR E. MASSA; FL¨¢VIO GARCIA; MARIA JESUS MARTINEZ-LOPE,; JOSE A. ALONSO
Campinas, SP, Brasil
Workshop; 20ª Reunion Anual do Usuarios- RAU; 2010
Laboratorio Nacional de Luz Sincrotron
Most perovskites at ambient pressure have lattice distortions departing from the ideal cubic structure that implies an octahedral orientation proclivity, by tilting and rotation, toward lower symmetry space groups. In this report we comment on our very preliminar results on reverting this trend by applying high enough quasi-hydrostatic pressure to orthorhombic NdNiO3 and PrNiO3 perovskites. These compounds undergo a metal-insulator transition with decreasing temperature at TIM ¡Ö 200 K and TIM ¡Ö 140 K, respectively. It is known that applied pressure induces a downshift of the TIM temperature. In our studies, at the DXAS beamline, we monitored the Ni K-edge aiming to observe changes in the pre-edge structure and oxygen nearest neighbors that might denote changes in the electronic or lattice configurations in the room temperature metallic phase. Our preliminary results on applying quasi-hydrostatic pressure up to about 10 Gpa using a conventional diamond anvil cell at room temperature yield a remarkable increase in the pre-edge structure of the Ni K-edge toward a rhombohedral phase .We attribute this to the likelhhod of having pressure altered the Ni pre-edge peak that it is associated with transitions from the Ni 1s to 3d states mixed with the oxygen 2p orbital in an increased hybridization pattern.