Uniaxial Strain-Controlled Ferroelastic Domain Evolution in BiFeO₃.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Ferroelectricity

Background:

• Epitaxial BiFeO3 (BFO) thin films exhibit ferroelastic domain structures.
• Understanding ferroelastic domain evolution under mechanical stress is crucial for device applications.

Purpose of the Study:

• To investigate the impact of uniaxial tensile strain on ferroelastic domain dynamics in (001)-oriented BFO thin films.
• To correlate nanoscale polarization changes with applied strain using in situ characterization.

Main Methods:

• Utilized piezoresponse force microscopy (PFM) combined with a novel bending stage for in situ tensile strain application and characterization.
• Observed nanoscale polarization-strain correlations and domain wall motion under varying tensile strain.

Main Results:

• Ferroelastic domains with in-plane polarization parallel to the tensile strain expanded, while those with orthogonal polarization contracted.
• Domain switching involved significant domain wall roughening and reversible, strain-induced polarization rotations.
• Films with long-range ordered domains showed greater susceptibility to strain compared to short-range ordered domains.

Conclusions:

• Tensile strain reversibly controls ferroelastic domain structure and polarization in BFO thin films.
• Strain-induced polarization rotation offers a pathway to tune coupled functionalities, including magnetism, in multiferroic BFO.