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

Q Li,S V Kalinin,R K Vasudevan,N Laanait,N Balke,Y Cao,P Maksymovych,A Tselev,L Q Chen,F Xue,P Yu

doi:10.1038/ncomms9985

Abstract

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 two- to three-fold enhancement of local piezoresponse. Coupled with phase-field modelling, we also addressed the influence of polarization switching and mesoscopic structural heterogeneities (for example, domain walls) on the kinetics of this phase transition, thereby providing fresh insights into the morphotropic phase boundary in ferroelectrics. Furthermore, 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 the utilization of the soft modes underlying successive ferroelectric phase transitions.

Highlights

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
Pivotal to the continued development of ferroelectrics is a deep understanding of their structural À dynamics relationship, which is conventionally separated into lattice and domain structure levels[4]
Scattering techniques based on X-ray/neutron and electron probes are capable of resolving subtleties in crystal structure and lattice dynamics near the morphotropic phase boundary (MPB) and allow in situ tracking of their response to external stimuli; these techniques generally fall short of capabilities to correlate structural dynamics with realspace microstructures, especially regarding domain structures

Summary

Introduction

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. Scattering techniques based on X-ray/neutron and electron probes are capable of resolving subtleties in crystal structure and lattice dynamics near the MPBs and allow in situ tracking of their response to external stimuli; these techniques generally fall short of capabilities to correlate structural dynamics with realspace microstructures, especially regarding domain structures To this end, piezoresponse force microscopy (PFM) has emerged as a primary tool for imaging electromechanical properties of materials with nanoscale resolution[18], and PFM spectroscopy has been developed in some forms enabling local probing of polarization switching dynamics[19,20,21]. BFO in the stability field of R-phase is to be considered instead

Methods

Results

Conclusion