Preparation, Structure and Giant Magnetoresistance of Electrodeposited Fe-Co/Cu Multilayers

Abstract

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...

Simple electrodepositing of CoFe/Cu multilayers: Effect of ferromagnetic layer thicknesses

“…For the multilayer deposition with reliable layer thickness, optimal potentials of the cathode have to be established where the dissolution and the co-deposition of the metal ions in the electrolyte can take place [8]. To determine these potentials, cyclic voltammograms (CV) can be used to establish the value of E Cu EC and E CoFe EC [22].…”

“…Especially, the GMR technology has been used in the field of microelectromechanical systems (MEMS), magnetoresistive sensor and data storage technology [3][4][5]. For the production of these kind of materials, there are lots of production technique such as sputtering, molecular beam epitaxy requiring ultra high vacuum and expensive [1,2] but electrodeposition are most commonly used due to its simplicity, fastness and inexpensiveness [6][7][8].…”

“…Therefore, when they are substituted into the magnetic multilayers, the multilayers can gain the low coercivity [8] and hence soft magnetic properties. Following the GMR discovery of Fe/Cr multilayers [1], the GMR has been observed in the multilayers such as Co/Cu [6,9], Ni-Fe/Cu [10] and CoFe/Cu [11,12] that have been prepared with a dc magnetron sputtering system or ion beam sputter system under ultra high vacuum.…”

“…Therefore, the coupling between adjacent layers has to be lower to obtain GMR in the lower magnetic field such as multilayers and spin valves. For the CoFe/Cu multilayers produced by the electrodeposition, there are some reports on the dependence of their GMR and its sensitivity on ferromagnetic or non-magnetic layers thicknesses [8,[14][15][16][17][18][19][20][21]. Non-magnetic layer dependence of deposition potential were studied by Toth et al [8].…”

Development of Giant Magnetoresistance Material Based on Cobalt Ferrite

“…Until now, the GMR material is still experience the process of research and development by the researcher. These materials are; metal [1], alloy [2,3], semiconductors [4], organic semiconductors [5] and magnetic oxide [6,7].…”