PERPENDICULAR CONDUCTANCE AND MAGNETIC COUPLING IN EPITAXIAL FE MGO/FE(100) TRILAYERS/

A series of Fe/MgO/Fe(100) trilayer structures with MgO thicknesses ra nging from 12 to 1000 Angstrom was grown at 75 degrees C by molecular beam epitaxy. The structures are all epitaxial, and for MgO thicknesse s 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. Per pendicular transport measurements show ohmic current-voltage character istics with high conductance up to 1000 Angstrom MgO interlayer thickn esses, indicating that the coupling is not due to spin-dependent tunne ling. Investigations of the growth morphology reveal the existence of ferromagnetic bridges across the MgO layer. (C) 1997 American Institut e of Physics.