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Ferroelectric Metal in Tetragonal BiCoO3/BiFeO3 Bilayers and Its Electric Field Effect
Li Yin1, Wenbo Mi1, Xiaocha Wang2
1Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology, Faculty of Science, Tianjin University, Tianjin, 300072, China.
Abstract:
By first-principles calculations we investigate the electronic structure of tetragonal BiCoO3/BiFeO3 bilayers with different terminations. The multiferroic insulator BiCoO3 and BiFeO3 transform into metal in all of three models. Particularly, energetically favored model CoO2-BiO exhibits ferroelectric metallic properties, and external electric field enhances the ferroelectric displacements significantly. The metallic character is mainly associated to eg electrons, while t2g electrons are responsible for ferroelectric properties. Moreover, the strong hybridization between eg and O p electrons around Fermi level provides conditions to the coexistence of ferroelectric and metallic properties. These special behaviors of electrons are influenced by the interfacial electronic reconstruction with formed Bi-O electrovalent bond, which breaks OA-Fe/Co-OB coupling partially. Besides, the external electric field reverses spin polarization of Fe/Co ions efficiently, even reaching 100%.
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