Electric-field-induced structural modulation of epitaxial BiFeO3 multiferroic thin films as studied using X-ray microdiffraction

An in situ method, called synchrotron x-ray microdiffraction, was introduced to examine the electric-field-induced structural modulation of the epitaxially grown pseudotetragonal BiFeO3 thin film. To evaluate the d spacing (d(001)) from the measured intensity contour in the 2 theta-chi space, the peak position in each diffraction profile was determined by applying two-dimensional Lorentzian fitting. By tracing the change of d spacing as a function of the applied electric field and by examining the Landau free energy function for P4mm symmetry, the authors were able to estimate the two important parameters that characterize the field-induced structural modulation. The estimated linear piezoelectric coefficient (d(33)) at zero-field limit is 15 pm/V, and the effective nonlinear electrostrictive coefficient (Q(eff)) is as low as similar to 8.0x10(-3) m(4)/C-2. (c) 2007 American Institute of Physics.