X-Ray and neutron reflectivity investigations of Co/Cu multilayers

We have studied the effect of low-energy ion beam etching of silicon (1 0 0) substrates on the magneto-transport and structural properties of sputter deposited cobalt/copper multilayers. The films had a nominal structure of 16*{1 nm Co/2.1 nm Cu} + 1 nm Pt placing them on the second peak of the oscillatory coupling curve. We show that, as the etching energy is increased from 0 to 1500 eV, the giant magnetoresistance (GMR) decreases from about 19% to about 1%. This is attributed to subtle changes in the him microstructure causing the destruction of antiferromagnetic coupling between the magnetic layers. We present reflectivity and X-ray diffraction data which suggest that Fermi surface effects in the bulk drive the changes in GMR. However, we conclude that spin-dependent scattering at the interfaces may yet be a significant factor and suggest that the interfacial structure be examined more closely using diffuse reflectivity techniques. (C) 1998 Elsevier Science B.V. All rights reserved.