STUDIES OF INTERLAYER EXCHANGE COUPLING IN FE CU/FE ULTRATHIN HETEROSTRUCTURES/

The interlayer exchange coupling has been investigated in trilayer str uctures where two coupled Fe layers were separated by a modified Cu sp acer. The multilayer heterostructures investigated in this article hav e the following general structure: Fe1/kCu/lX(c)Cu(1-c)/mCu/Fe-2, wher e XcCu1-c indicates one atomic layer of Cu atoms alloyed with foreign X atoms of concentration c. Fe-1 and Fe-2 indicate bottom and top ferr omagnetic iron layers, respectively. k, l, and m represent the number of atomic layers (AL) yielding a total spacer thickness of(k + l + m) AL. The ultrathin films were grown using a molecular beam epitaxy syst em. Atoms X (Fe,Fe-57,Cr,Ag) were codeposited simultaneously with the Cu atoms to create an alloyed layer. Foreign atoms were introduced in the spacer to study their effect on the direct interlayer exchange cou pling between the outside Fe layers mediated by the valence electrons of the Cu spacer. The ferromagnetic resonance, magneto-optical Kerr ef fect, and Brillouin light scattering techniques were employed to deter mine the exchange coupling in these structures. Mossbauer spectroscopy was used to identify the magnetic state of the Fe-57 atoms in the all oyed (FecCu1-c)-Fe-57 layer. The results have shown that the presence of foreign atoms inside the Cu spacer significantly decreases the bili near antiferromagnetic coupling between the Fe layers by creating a po tential barrier for the valence Cu electrons. More significantly, the exchange coupling showed a very strong dependence on the magnetic stat e of the foreign atom. For high concentrations of Fe in the spacer, th e coupling was found to be ferromagnetic due to partial magnetic order ing of the iron atoms. (C) 1997 American Institute of Physics.