Giant elastic tunability in strained BiFeO3 near an electrically induced phase transition

• Published in: Nature communications Vol. 6; no. 4
• Main Authors: Yu, Pu, Vasudevan, Rama K., Tselev, Alexander, Xue, Fei, Chen, Long -Qing, Maksymovych, Petro, Kalinin, Sergei V., Balke, Nina, Li, Q., Cao, Y., Laanait, N.
• Format: Journal Article
• Language: English
• Published: United States Nature Publishing Group 24.11.2015
• Subjects: MATERIALS SCIENCE
• ISSN: 2041-1723; 2041-1723

Elastic anomalies are signatures of phase transitions in condensed matters and have traditionally been studied using various techniques spanning from neutron scattering to static mechanical testing. Here, using band-excitation elastic/piezoresponse spectroscopy, we probed sub-MHz elastic dynamics of a tip bias-induced rhombohedral–tetragonal phase transition of strained (001)-BiFeO3 (rhombohedral) ferroelectric thin films from ~103 nm3 sample volumes. Near this transition, we observed that the Young's modulus intrinsically softens by over 30% coinciding with 2-3 folds enhancement of local piezoresponse. Coupled with phase-field modeling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (e.g., domain walls) on the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary (MPB) in ferroelectrics. Moreover, the giant electrically tunable elastic stiffness and corresponding electromechanical properties observed here suggest potential applications of BiFeO3 in next-generation frequency-agile electroacoustic devices, based on utilization of the soft modes underlying successive ferroelectric phase transitions.