The Effect of Fe Content in Electrodeposited CoFe/Cu Multilayers on Structural, Magnetic and Magnetoresistance Characterizations

Abstract

A series of CoFe/Cu multilayers were electrodeposited on Ti substrates from the electrolytes containing their metal ion under potentiostatic control, but the Fe concentration in the electrolytes was changed from 0.0125 M to 0.2 M. The deposition was carried out in a three-electrode cell at room temperature. The deposition of Cu layers was made at a cathode potential of -0.3 V with respect to saturated calomel electrode (SCE), while the ferromagnetic CoFe layers were deposited at -1.5 V versus SCE. The structural studies by X-ray diffraction revealed that the multilayers have face-centered-cubic structure. The magnetic characteristics of the films were investigated using a vibrating sample magnetometer and their easy-axis was found to be in film plane. Magnetoresistance measurements were carried out using the Van der Pauw method at room temperature with magnetic fields up to +/- 12 kOe. All multilayers exhibited giant magnetoresistance (GMR) and the GMR values up to 8% were obtained.

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

“…However, the decrease reported by Tekgül et al 10 is much slower than that was observed in the present study. The reported MR values are also higher.…”

“…The preset nominal Co-Fe and Cu layer thicknesses were kept constant at 6 nm and 4.5 nm, respectively. The applied deposition potentials were E FeCo (SCE) = −1.5 V and E Cu (SCE) = −0.3 V. The Cu deposition potential is even more positive than the one used by Kakuno et al; 9 therefore, an even stronger dissolution of the magnetic layer and, thus, even larger layer thickness changes with respect to the nominal values can be expected for the multilayers investigated by Tekgül et al 10 These authors have also analyzed their multilayers and the resulting Fe/Co ratios in their magnetic layers with varying Fe concentrations in the bath exhibit a fairly good agreement with our data as shown in Fig. 4 (although the comparison may not be completely valid since the current density used in their work for magnetic layer deposition is not known).…”

“…The different preparation conditions will not enable us to make a straightforward comparison between the previous and present GMR results; however, to provide a basis for the discussion of the differences in the observed GMR behavior, it may be useful to summarize first briefly the preparation conditions and structural features reported in the previous studies. 9,10 Kakuno et al 9 investigated the GMR of ED Fe-Co-Cu/Cu multilayers prepared with typically 20 bilayers with a potentiostatic/potentiostatic (P/P) pulse combination from a solution containing 0. potentials was given, it was only noticed that at these electrode potentials the Fe-Co electrodeposits exhibited a very shiny surface whereas the Cu electrodeposits a slightly opaque surface. As to the Fe-Co layer deposition potential, its actual value does not play an important role in determining the properties of the magnetic layer.…”

“…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.…”

“…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.…”