Engineering and investigation of the interlayer exchange coupling in bcc Fe/Cu/Fe(001) structures

This thesis presents experimental and theoretical studies of interlayer exchange coupling between two Fe layers separated by a modified Cu spacer. The purpose of the experimental and theoretical work was to determine how the interlayer exchange coupling was affected when the central atomic layer of the pure Cu spacer was replaced by one atomic layer of a foreign X element or an X-Cu alloy. The multilayer structures have the general form: Fe/Cu/X cCu1-c/Cu/Fe where XcCu1-c indicates 1 atomic layer of foreign atoms X (Cr, Ag, Fe or Fe57) of concentration c alloyed with Cu atoms. The ultrathin films were grown using Molecular Beam Epitaxy. The exchange coupling was determined from ferromagnetic resonance and Magneto-Optical Kerr Effect and compared to Brillouin Light Scattering studies performed by Prof J. F. Cochran. The magnetic state of the 57Fe atoms was obtained from Mossbauer studies performed by Prof P. Schurer. The experimental results showed that the presence of foreign atoms inside the Cu spacer significantly decreases the antiferromagnetic bilinear exchange coupling of the pure Cu spacer. In the case of magnetically ordered Fe the coupling changed its sign to ferromagnetic. Any desired value of the interlayer exchange coupling could be engineered by varying the type and concentration of the foreign atoms. The first principles theoretical calculation were performed using the Layer Korringa-Kohn-Rostoker method. Both the experiment and theory showed that the exchange coupling is primarily affected by the magnetic state of the foreign atoms, and secondarily by their electronic structure and lattice relaxations.