Enhanced Ferroelectric Polarization in Epitaxial BiFeO3-BiMg2/3Nb1/3O3 Films

Remanent polarization is a key parameter of a ferroelectric material. A large remanent polariza-tion is favorable for various ferroelectric applications. Here, we report a large remanent polarization of 116.8 mu C cm-2 observed in BiMg2/3Nb1/3O3 (BMN)-modified BiFeO3 (BFO) thin films, epitaxially deposited on (001)-oriented SrTiO3 substrates buffered with La2/3Sr1/3MnO3 electrodes. Combined exper-imental analyses and first-principles calculations reveal that the incorporation of 10 mol % BMN into BFO increases both the intrinsic and extrinsic contributions, resulting in doubled polarization. The intrin-sic polarization calculated for BFO-BMN is larger than that of BFO due to enhanced ionic displacements. Compared with epitaxial BFO films in a rhombohedral structure with an interaxial angle of alpha = 89.72 degrees and quasitetragonal c/a =1.018, the epitaxial BFO-BMN films become more tetragonal-like, with alpha = 89.91 degrees and c/a =1.037. Moreover, a unique rotated twinning-domain structure is developed in the BFO-BMN thin films, further increasing the out-of-plane polarization by rotating the [111] direction toward the film's normal. These results provide additional opportunities to increase ferroelectric polarization through composition engineering.

Automated summary

We have deposited BMN-modified BFO thin films on (001)-oriented SrTiO3 substrates buffered with La2/3Sr1/3MnO3 electrodes and observed a large remanent polarization of 116.8 mu C cm-2. Experimental analyses and first-principles calculations show that the inclusion of 10 mol % BMN increases both the intrinsic and extrinsic contributions, resulting in a doubled polarization. Compared to rhombohedral BFO films, the epitaxial BFO-BMN films exhibit a more tetragonal-like structure and a unique rotated twinning-domain structure, enhancing the out-of-plane polarization.