EXCHANGE COUPLING IN SPUTTERED GIANT MAGNETORESISTANCE NIFE CU/COFE/CU MULTILAYERS/

We will report on the exchange coupling, magnetoresistance (MR) and fi lm structure in the system NiFe/Cu/CoFe/Cu as a function of multilayer number (bilayers=6 to 20) and Cu spacing (5 to 31 Angstrom). The mult ilayers were prepared by sputter deposition and investigated by x-ray diffraction (XRD), atomic force microscopy(AFM), vibrating sample magn etometry (VSM), ferromagnetic resonance (FMR), and standard MR methods . The exchange coupling, H-ex, and MR are shown to vary with Cu spacin g. The XRD data indicates the multilayer structure is evolving through at least the first 20 bilayers. AFM measurements suggest subtle varia tions in interface quality and a rms roughness near 0.4 nm. These vari ations in structure are manifested in the FMR and MR. Multilayers with Cu spacers >11 Angstrom generally show the expected two FMR peaks. So me multilayers show three peaks indicating defects within the multilay er. These defects can be viewed as the elusive ''pinholes'' which act to ferromagnetically short the magnetic layers together. This demonstr ates that FMR provides very valuable information about defects in noni deal multilayers which is critical to our understanding and applicatio ns of giant magnetoresistance (GMR) systems. (C) 1996 American Institu te of Physics.