Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 20: Metall-Isolator-Überg
änge
TT 20.5: Vortrag
Mittwoch, 10. März 2004, 15:30–15:45, H18
Pressure-induced metal-insulator transition in rare earth nickelates RNiO3 — •R. Lengsdorf1, J.A. Alonso2, M.J. Martinez-Lope2, M. Amboage Castro2, and M.M. Abd-Elmeguid1 — 1II. Physikalisches Institut Universität zu Köln, Zülpicherstr. 77, 50937 Köln, Germany — 2Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, E-28049 Madrid, Spain
We report on the effect of pressure up to 25 GPa on the electronic and structural properties (electrical resistance and x-ray diffraction) of two selected antiferromagnetic charge transfer insulators EuNiO3 (orthorhombic, TN = 220 K) and LuNiO3 (monoclinic, TN = 130 K) which undergo a thermal-induced insulator-metal transition (IMT) at TIM = 460 K and 599 K, respectively. The IMT in LuNiO3 is connected with a monoclinic-to-orthorhombic structural phase transition, whereas the orthorhombic structure of EuNiO3 remains unchanged.
In both systems we find a pressure-induced IMT at a critical pressure of about 6 GPa, while the crystal structure remains unchanged. Structural phase transitions are observed at much higher pressures: EuNiO3 orthorhombic to rhombohedral at 12 GPa and LuNiO3 at 16 GPa. The experimental results are explained in terms of a pressure-induced increase of the 3d-2p-3d orbital hybridization as a result of increasing the Ni-O-Ni bonding angle with increasing pressure. The influence of the charge transfer between localized Ni and O states on the pressure-induced IMT in LuNiO3 is also discussed.