We have made epitaxial and polycrystalline thin films of multiferroic ${\mathrm{BiFeO}}_3$ on different substrates [(001) and (111) ${\mathrm{SrTiO}}_3$, (001) and (111) ${\mathrm{LaAlO}}_3$, (001) $\mathrm{MgO}$, and (0001) sapphire] by pulsed-laser deposition. We investigated the second harmonic generation (SHG) in these films and find that the SHG was smallest in epitaxially grown films on (001) ${\mathrm{SrTiO}}_3$ and largest in epitaxial films grown on (111) ${\mathrm{SrTiO}}_3$ and (111) ${\mathrm{LaAlO}}_3$. We discuss these results in terms of the crystal structure as well as the film microstructure.

• Received 25 October 2005

DOI:https://doi.org/10.1103/PhysRevB.73.092408