Regensburg 2000 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 38: Postersitzung

DS 38.39: Poster

Dienstag, 28. März 2000, 09:30–17:30, Poster B

Effect of the epitaxial strain on the MI transition in perovskite films — •Oleg Gorbenko¹, Mikhail Novozhilov¹, Igor Graboy¹, Vadim Amelitchev¹, Andrey Kaul¹, Georg Wahl², and Oliver Stadel² — ¹Chemistry Dpt., Moscow State University, 119899 Moscow, Russia — ²IOPW, TU Braunschweig, Bienroder Weg 53, 38108 Braunschweig

Thin films of the various perovskites R_1−xA_xMO₃ (where R - rare earth cation, A -alkaline earth cation, M - transition metal cation like Mn, Co, Cr, Ni, or Ru) were grown with high epitaxial quality on the single crystalline insulating perovskite substrates by MOCVD. We demonstrate with X-ray diffraction and HREM that the film-substrate lattice mismatch gives rise to the epitaxial lattice strain in thin perovskite films rather than to the formation of the misfit dislocations. The epitaxial lattice strain causes anisotropic variation of the valence angles M-O-M and chemical bond lengths. Resistivity measurements demonstrate that such anisotropic pressure produces huge effect on the metal-insulator transition in the conducting perovskite films. The behavior of the perovskite materials with an insulating ground state (like RNiO₃ ) and that of the perovskite materials with a metallic ground state (like (La_1−xPr_x)_0.7Ca_0.3MnO₃ ) are compared and analysed in the frame of tight binding model. The temperature hysteresis phenomena in the strained epitaxial films including reentrant metal-insulator phase transition are discussed.