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arXiv · 0705.2883

The beta Phase of Multiferroic Bismuth Ferrite and its beta-gamma Metal-Insulator Transition

R. Palai·R. S. Katiyar·H. Schmid·P. Tissot·S. J. Clark·J. Robertson·S. A. T. Redfern·J. F. Scott
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Abstract

We show that epitaxial (001) thin films of multiferroic bismuth ferrite BiFeO3 are monoclinic at room temperature instead of tetragonal or Rhombohedral as reported earlier . We report a orthorhombic order-disorder beta-phase between 820C and 950C contrary to the earlier report. The transition sequence monoclinic-orthorhombic phase in (001)BiFeO3 thin film (rhombohedral-orthorhombic transition in single crystal) resembles that of BaTiO3 or PbSc1/2Ta1/2O3. The transition to the cubic $γ$-phase causes an abrupt collapse of the bandgap toward zero (insulator-metal transition) at the orthorhombic-cubic beta-gamma transition around 950C. This transition is similar to the metal-insulator transition in Ba0.6K0.4BiO3.

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R. Palai, R. S. Katiyar, H. Schmid, P. Tissot, S. J. Clark, J. Robertson, S. A. T. Redfern, J. F. Scott. 2007-07-13. The beta Phase of Multiferroic Bismuth Ferrite and its beta-gamma Metal-Insulator Transition. https://doi.org/10.1103/physrevb.77.014110

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