Coherent x-ray diffraction imaging of photo-induced structural changes in BiFeO₃nanocrystals

Abstract

Multiferroic materials that exhibit coupling between ferroelectric and magnetic properties are of considerable utility for technological applications and are also interesting from a fundamental standpoint. When reduced to the nanoscale, multiferroic materials often display additional functionality that is dominated by interfacial and confinement effects. Bismuth ferrite (BiFeO 3 ) is one such material with room temperature anti-ferromagnetic and ferroelectric ordering. Optical excitation of BiFeO 3 crystals results in an elastic structural deformation of the lattice with a fast response on the pico-second time scale. Here we report on dynamic measurements to investigate the structural properties of BiFeO 3 nanoscale crystals using laser excitation and three-dimensional Bragg coherent x-ray diffraction imaging. Tensile strain beyond 8´-10 2 was observed predominantly at the surface of the nanoscale crystal as evidenced in the reconstructed phase information and was correlated to photo-induced lattice deformation.

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