No systematic studies have been carried out on the giant magnetoresistance (GMR) of electrodeposited (ED) Fe-Co/Cu multilayers since the elaboration of a method for the optimization of the Cu layer deposition potential. In this paper, we present results on the electrochemical optimization of the Cu layer deposition potential which was found to depend on the relative iron concentration in the bath. An X-ray diffraction study of ED Fe 5 Co 95 (1.5 nm)/Cu(d Cu ) multilayers with d Cu ranging from 0.8 nm to 10 nm revealed an fcc structure. For most of the multilayers, weak superlattice satellite reflections could be identified. The room-temperature magnetoresistance was studied in detail as a function of the individual layer thicknesses. Multilayers with Cu layer thicknesses above about 1.5 nm were found to exhibit a GMR behavior with a maximum GMR of about 5% and a typical saturation field of 1 kOe. The GMR magnitude decreased with increasing Fe-content in the magnetic layer. The spacer layer thickness evolution of the MR data was established in detail after separating the ferromagnetic and superparamagnetic GMR contributions and no oscillatory GMR was found. A comparison with literature data on both physically deposited and ED Fe-Co/Cu multilayers is also made. Since bulk Fe-Co alloys have good soft magnetic properties, 1 multilayers with this kind of alloy as the magnetic layer can have favorably low coercivity. A detailed giant magnetoresistance study (GMR) study of sputtered TM/Cu multilayers by using binary and ternary alloys of Fe, Co and Ni as magnetic layers has been carried out by Miyazaki et al.2 who also mapped out the anisotropic magnetoresistance (AMR) of bulk alloys of the Fe-Co-Ni system. As to the GMR of physically deposited Fe-Co/Cu multilayers, it was shown that they can, indeed, have a significant room-temperature GMR (Refs. 2 and 3) with fairly low saturation fields.
3Inomata and Saito 3 investigated sputtered Fe-Co/Cu multilayers with Fe-concentrations of 10, 20 and 50%. In their study, the Cu layer thickness was varied between 0.9 and 3.8 nm and three oscillatory GMR peaks were found as a function of the spacer layer thickness. Rafaja et al. 4 found about 25% GMR on sputtered [Fe 10 Co 90 (1.1 nm)/Cu(2.2 nm)]x20 multilayers but a detailed study on the influence of the individual layer thicknesses was not carried out. Gangopadhyay et al.5 also studied sputtered Fe 10 Co 90 /Cu multilayers. The Cu layer thickness was varied between 0.5 and 3.1 nm and an oscillatory GMR was found, but contrary to the typical result on sputtered multilayers, the second peak was found to be the larger.There are contradictory experimental data in the literature on physically deposited FM/Cu multilayers, whether a pure Co magnetic layer or a Fe-Co alloy shows larger GMR value. Kataoka et al. 6 and Inomata and Saito 3 present data according to which for [Fe 20 Co 80 (1.0 nm)/Cu(1.0 nm)]x15 multilayers the GMR is higher than for multilayers with pure Co as magnetic layer, while the work of Miyazaki et al. 7 shows that...