  Epitaxial BiFeO3/SrRuO3 superlattices have been grown by pulsed laser
deposition on a (001) oriented LaAlO3 substrate and probed by X-ray diffraction
and Raman spectroscopy. To investigate the structural competition between
rhombohedral BiFeO3 and orthorhombic SrRuO3 the total thickness of all SLs was
kept constant and the bilayer thickness (period) {\Lambda} was varied. The
interlayer strain effects are therefore tuned from large strain effects (short
{\Lambda} period) to quasi-relaxed structure (large {\Lambda}). A complementary
investigation using X-ray diffraction and phonon dynamics hints to change from
a rhombohedral to a tetragonal structure in the superlattices with the increase
of the interlayer strain effect.
