  A previous study of the growth conditions has shown that single-phase BiFeO3
thin films can only be obtained in a narrow pressure-temperature window and
that these films display a weak magnetic moment. Here we study in more detail
the structure and the magnetism of single-phase BiFeO3 films by means of
reciprocal space mapping, Raman spectroscopy and neutron diffraction. X-ray and
Raman data suggest that the BiFeO3 structure is tetragonal for 70 nm-thick
films and changes to monoclinic for 240 nm-thick films, thus remaining
different from that of the bulk (rhombohedral) structure. In the 240 nm
monoclinically distorted film neutron diffraction experiments allow the
observation of a G-type antiferromagnetic order as in bulk single crystals.
However, the satellite peaks associated with the long-wavelength cycloid
present in bulk BiFeO3 are not observed. The relevance of these findings for
the exploitation of the magnetoelectric properties of BiFeO3 is discussed.
