Iron-oxide interlayer existing in Ba-ferrite/sapphire(001) films grown by sputtering

We revealed the existence of a very thin (similar to 50 Angstrom thick) epi taxial. iron-oxide interlayer in amorphous Ba-ferrite thin films on sapphir e(001) using synchrotron x-ray scattering. Depending on the sputtering gase s used in radio frequency sputtering deposition, two different iron-oxide i nterlayers were formed; non-magnetic alpha-Fe2O3 interlayer by pure Ar gas and ferromagnetic Fe3O4 interlayer by Ar-10% O-2 gas mixture. The alpha-Fe2 O3 interlayer much more promoted the crystallization of amorphous Ba-ferrit e, compared to the Fe3O4 interlayer. We suggest that the interlayer existin g between amorphous Ba-ferrite and sapphire substrate greatly contributes t o the reduction of the activation energy for the crystallization of amorpho us Baferrite film.