  The giant magnetoresistance (GMR) was investigated for electrodeposited Co/Cu
multilayers. In order to better understand the formation of individual layers
and their influence on GMR, multilayers produced by two different deposition
strategies were compared. One series of Co(2 nm)/Cu(tCu) multilayers with tCu
ranging from 0.5 nm to 6 nm was produced with the conventional two-pulse
plating by using a galvanostatic/potentiostatic (G/P) pulse combination for the
magnetic/non-magnetic layer deposition, respectively, whereby the Cu layer
deposition was carried out at the electrochemically optimized potential.
Another Co(2 nm)/Cu(tCu) multilayer series with the same tCu range was prepared
with the help of a G/P/G pulse combination. In this latter case, first a
bilayer of Co(2 nm)/Cu(6 nm) was deposited in each cycle as in the G/P mode
after which a third G pulse was applied with a small anodic current to dissolve
part of the 6 nm thick Cu layer in order to ensure the targeted tCu value. The
comparison of the two series revealed that the G/P/G pulse combination yields
multilayers for which GMR can be obtained even at such low nominal Cu layer
thicknesses where G/P multilayers already exhibit bulk-like anisotropic
magnetoresistance only. Surface roughness measurements by atomic force
microscopy revealed that the two kinds of pulse combination yield different
surface roughness values which correlate with the structural quality of the
multilayers as indicated by the absence or presence of multilayer satellite
reflections in the X-ray diffraction patterns. The results of multilayer
chemical analysis revealed that mainly an increased Cu content of the magnetic
layer is responsible for the onset of SPM regions in the form of Co
segregations in the G/P/G multilayers with small Cu layer thicknesses.
