Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers Prepared by Two-Pulse (G/P) and Three-Pulse (G/P/G) Plating

Rajasekaran, N.; Pogány, L.; Révész, Ádám; Tóth, Bence; Mohan, S.; Péter, László; Bakonyi, I.

doi:10.1149/2.066406jes

Cited by 13 publications

(23 citation statements)

References 32 publications

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“…1 and 2 in order to deduce the experimental bilayer length XRD and the results are summarized in Fig. 3 Co/Cu multilayers, 26 including also data derived with the help of a more sophisticated full-profile fitting procedure 13,14 or even direct cross-sectional TEM imaging.…”

Section: Results On Multilayers With Cu Layers Depositedmentioning

confidence: 99%

“…In general, the bilayer lengths derived from either TEM or XRD were in fairly good agreement with the nominal values, the experimental data being typically 10 to 20% higher. 13,14,[26][27][28] In order to trace out the layer thickness changes in the fourth set of multilayers, the overall composition of the multilayers also had to be determined. This analysis was carried out by energy dispersive X-ray fluorescence (EDXRF) method with an XGT-HORIBA-5200 instrument.…”

Section: Methodsmentioning

confidence: 99%

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Giant Magnetoresistance and Structure of Electrodeposited Co/Cu Multilayers: The Influence of Layer Thicknesses and Cu Deposition Potential

Rajasekaran

Mani

Tóth

et al. 2015

J. Electrochem. Soc.

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The giant magnetoresistance (GMR) and structure was investigated for electrodeposited Co/Cu multilayers prepared by a conventional galvanostatic/potentiostatic pulse combination from a pure sulfate electrolyte with various layer thicknesses, total multilayer thickness and Cu deposition potential. X-ray diffraction (XRD) measurements revealed superlattice satellite reflections for many of the multilayers having sufficiently large thickness (at least 2 nm) of both constituent layers. The bilayer repeats derived from the positions of the visible superlattice reflections were typically 10 -20% higher than the nominal values. The observed GMR was found to be dominated by the multilayer-like ferromagnetic (FM) contribution even for multilayers without visible superlattice satellites. There was always also a modest superparamagnetic (SPM) contribution to the GMR and this term was the largest for multilayers with very thin (0.5 nm) magnetic layers containing apparently a small amount of magnetically decoupled SPM regions. No oscillatory GMR behavior with spacer thickness was observed at any magnetic layer thickness. The saturation of the coercivity as measured by the peak position of the MR(H) curves indicated a complete decoupling of magnetic layers for large spacer thicknesses. The GMR increased with total multilayer thickness which could be ascribed to an increasing SPM contribution to the GMR due to an increasing surface roughness, also indicated by the increasing coercivity. For multilayers with Cu layers deposited at more and more positive potentials, the GMR FM term increased and the GMR SPM term decreased. At the same time, a corresponding reduction of surface roughness measured with atomic force microscopy indicated an improvement of the multilayer structural quality which was, however, not accompanied by an increase of the superlattice reflection intensities. The present results underline that whereas the structural quality as characterized by the surface roughness generally correlates fairly well with the magnitude of the GMR, the microstructural features determining the amplitude of superlattice reflections apparently do not have a direct influence on the GMR. Due to the large giant magnetoresistance (GMR) effect observed in physically deposited Co/Cu multilayers, 1-3 a lot of efforts have been devoted to the study of GMR also on electrodeposited (ED) Co/Cu multilayers (for detailed references, see a recent review).4 A variety of baths have been used for the preparation of ED Co/Cu multilayers, 4 the simplest one containing merely CoSO 4 and CuSO 4 . Over the last two decades, numerous reports have been published on studying the GMR characteristics of ED Co/Cu multilayers from the pure sulfate bath (containing at most some buffering agents). [5][6][7][8][9][10][11][12][13][14][15] In this list of references, we have included only those works from the much larger number of reports 4 in which the ED Co/Cu multilayers were prepared from the sulfate bath at or close to the electrochemically optimized Cu depositi...

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Section: Results On Multilayers With Cu Layers Depositedmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Giant Magnetoresistance and Structure of Electrodeposited Co/Cu Multilayers: The Influence of Layer Thicknesses and Cu Deposition Potential

Rajasekaran

Mani

Tóth

et al. 2015

J. Electrochem. Soc.

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“…By contrast, in ED Co/Cu multilayers, [5][6][7][8][9] the GMR shows a monotonous increase with increasing Cu layer thickness up to about 4 to 5 nm; for thicker Cu layers, the GMR decreases again. The lack of oscillatory GMR was evidenced as a sign for the absence of a significant AF coupling.…”

mentioning

confidence: 81%

“…The bilayer thickness determined from the XRD data ( XRD ) is slightly larger than nom , as it is usually observed for ED Co/Cu multilayers. 9 In Eq. 1, the positions of two neighboring satellites are denoted as θ n and θ n+1 , whereas λ is the wavelength of the X-rays.…”

Section: Methodsmentioning

confidence: 99%

Influence of Ag Additive to the Spacer Layer on the Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers

Neuróhr

Péter

Pogány

et al. 2015

J. Electrochem. Soc.

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In order to explore the possible surfactant effect of Ag on the formation of electrodeposited multilayers, Co/Cu(Ag) multilayers were prepared by this technique and their structure and giant magnetoresistance (GMR) were investigated. The multilayers were deposited from a perchlorate bath with various amounts of Ag + ions in the solution for incorporating Ag atoms into the multilayer stack. Without Ag addition, secondary neutral mass spectroscopy (SNMS) indicated a well-defined composition modulation of the undermost Co/Cu bilayers. However, already at an Ag content as low as 1.8 at.% incorporated, SNMS showed a deterioration of the periodic multilayer structure. In agreement with the SNMS results, superlattice satellites were visible in the X-ray diffraction (XRD) patterns of the multilayers with up to 0.3 at.% Ag. The satellites were, however, very faint even for multilayers without Ag addition, indicating that the multilayers have high interface roughness and/or poor periodicity. In the absence of Ag and at the smallest Ag content investigated by XRD, a strong central multilayer peak and the weak superlattice satellites were complemented by weak diffraction maxima from non-periodic Co and Cu domains. In the Co/Cu(Ag) multilayer containing about 25 at.% Ag, i.e., nearly as much as Cu, XRD found a separate Ag(Cu) phase. In spite of the imperfect layered structure, a multilayer-type GMR behavior was observed in all samples up to about 10 at.% Ag incorporated in the multilayer stack. The GMR magnitude increased for Ag contents up to about 1 at.%, which implies that a small amount of Ag may have a beneficial effect through a slight modification of the layer growth and/or interface formation. However, for higher Ag contents beyond this level, the GMR was reduced in line with the structural degradation revealed by XRD and SNMS. For the highest Ag contents (above about 10 at.%), the GMR exhibited a behavior characteristic of a granular magnetic alloy, in agreement with the results of the structural study. One of the major obstacles hindering the realization of a high giant magnetoresistance (GMR) in electrodeposited (ED) ferromagnetic/non-magnetic (FM/NM) multilayers is that the nonmagnetic spacer layer cannot be electrodeposited as pinhole-free for layer thicknesses which are required to achieve high GMR and an oscillatory GMR behavior. 1 Sputtered Co/Cu multilayers 2-4 exhibit an oscillatory GMR and a room-temperature GMR of about 50% and 20% at about 1 and 2 nm Cu layer thicknesses, respectively. At these particular spacer thicknesses, a strong antiferromagnetic (AF) exchange coupling exists between the adjacent magnetic layers. It gives rise then to a large GMR effect since the AF coupling ensures an antiparallel alignment of the magnetizations of the neighboring magnetic layers in zero magnetic field. For spacer thicknesses between these so-called AF maxima, the exchange coupling is predominantly ferromagnetic. Thus, due to the parallel alignment of the layer magnetizations even in zero magnetic field, no GMR eff...

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“…Co-Cu multilayer or granular films are of great interest due to their high resistivity [1], magnetism and magneto-transport [2][3][4][5][6]. These excellent properties have brought interesting potential applications for magnetic read heads and sensors.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical preparation and magnetic properties of Co–Cu nanometric granular alloy films

et al. 2019

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A detailed electrodeposition of Co-Cu nanometric granular alloy films in citrate solution has been performed based on a galvanostatic technique. Electrochemical behaviour of the bath solution containing both Co 2+ and Cu 2+ was investigated by linear sweep voltammetry. Cathodic polarization curves indicated that high quality Co-Cu nanometric granular alloy films can be obtained at room temperature with a pH of 6 and current density equal to or more negative than − 1.0 mA cm −2. Magnetic properties of the films were measured at room temperature by the physical property measurement system. Magnetization curves of the as-prepared Co-Cu nanometric granular alloy films displayed superparamagnetism (SPM). However, after annealing at 450 • C for 1 h, magnetic property of the films changed from SPM to ferromagnetism. Meanwhile, the annealed Co-Cu nanometric granular alloy films showed an increase in saturation magnetization with the increase of the current density.

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Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers Prepared by Two-Pulse (G/P) and Three-Pulse (G/P/G) Plating

Cited by 13 publications

References 32 publications

Giant Magnetoresistance and Structure of Electrodeposited Co/Cu Multilayers: The Influence of Layer Thicknesses and Cu Deposition Potential

Giant Magnetoresistance and Structure of Electrodeposited Co/Cu Multilayers: The Influence of Layer Thicknesses and Cu Deposition Potential

Influence of Ag Additive to the Spacer Layer on the Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers

Electrochemical preparation and magnetic properties of Co–Cu nanometric granular alloy films

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