Giant magnetoresistance in electrodeposited Co₈₇Fe₁₃/Cu compositionally modulated alloys

Abstract

In this paper we report on the giant magnetoresistance effect and oscillatory exchange coupling in electrodeposited Co 87 Fe 13 /Cu compositionally modulated alloys. The alloys are compositionally modulated over nanometre length scales with ferromagnetic Co 87 Fe 13 (Cu) alloy layers and non-magnetic Cu layers. Co 87 Fe 13 /Cu multilayered thin films were electrodeposited from a single sulfate plating solution containing all metallic ions of interest under computer-controlled potentiostat switching on (111)-textured Cu buffers previously evaporated on Si(111). Electrodeposits present a polycrystalline character with coexistence of face-centred cubic (fcc) and hexagonal close-packed (hcp) structures. Magnetoresistance effects as high as 8% were observed at room temperature. The dependence of the magnetoresistance effect on Cu spacer layer thickness shows an oscillation period around 1.0 nm.

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

“…This means that a strong dissolution of the magnetic layer took place during the Cu deposition pulse and, thus, for each multilayer, the actual magnetic layer thicknesses were less than the nominal preset value and the reverse is true for the Cu layer. According to our previous experience with ED Co/Cu multilayers, 13,26 at the Cu deposition potential applied by Kakuno et al, 9 the layer thickness changes due to the magnetic layer dissolution during the Cu deposition pulse may be around 1 nm. This is especially important since the major objective of Kakuno et al 9 was to study the dependence of GMR on the Cu layer thickness.…”

“…By properly decomposing the GMR into FM and SPM contributions, it could be concluded that the GMR FM contribution does not exhibit an oscillatory GMR in ED Fe-Co/Cu multilayers as a function of the spacer layer thickness, in agreement with previous observations on various ED multilayers. [28][29][30][31][32][33][34][35] By a detailed analysis of the results of Kakuno et al 9 about an oscillatory GMR, it could be pointed out that their findings cannot be considered as reliably demonstrating such a behavior.…”

“…As to the magnetoresistance itself, the TMR component was only reported by Kakuno et al 9 Due to the magnetic softness of the Fe-Co alloys, the MR(H) curves of the ED Fe-Co/Cu multilayers saturated in magnetic fields around 0.5 kOe for sufficiently thick (2 to 4 nm) magnetic layers. However, for magnetic layer thicknesses at and below 1 nm, the MR(H) curve shape indicated an SPM-type behavior.…”

“…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.…”

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

“…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].…”