Perpendicular conductance and magnetic coupling in epitaxial Fe/MgO/Fe(100) trilayers

A series of Fe/MgO/Fe(100) trilayer structures with MgO thicknesses ranging from 12 to 1000 Angstrom was grown at 75 degrees C by molecular beam epitaxy. The structures are all epitaxial, and for MgO thicknesses below 75 Angstrom, the Fe layers are ferromagnetically coupled. The MgO spacer thickness dependence of the coupling energy shows a change in slope at 25 Angstrom; suggesting a change in growth morphology. Perpendicular transport measurements show ohmic current-voltage characteristics with high conductance up to 1000 Angstrom MgO interlayer thicknesses, indicating that the coupling is not due to spin-dependent tunneling. Investigations of the growth morphology reveal the existence of ferromagnetic bridges across the MgO layer. (C) 1997 American Institute of Physics.