Giant magnetoresistance and interlayer exchange coupling in Ni-Co/Cu multilayer films

Kubota, Hiroshi; Ishio, S.; Miyazaki, T.; Stadnik, Z. M.

doi:10.1016/0304-8853(94)90136-8

Cited by 46 publications

(38 citation statements)

References 23 publications

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“…3 indicate the approximate positions of the first three GMR maxima observed for sputtered fcc(111) Co/Cu multilayers. 5,56,57 The clear absence of an oscillatory GMR behaviour can be established for the present electrodeposited Co/Cu multilayers. Especially, there are no distinct features in the GMR magnitude at the usual positions of the AF maxima in the oscillatory interlayer exchange coupling.…”

Section: B Magnetoresistancesupporting

confidence: 57%

“…By contrast, for physically deposited multilayers MR saturation against the AF-coupling can usually be achieved well below 10 kOe even at the first AF maximum (spacer thickness around 1 nm), whereas at the second and third AF maximum the saturation field is of the order of a few hundred oersted only. 5,57,61 In order to understand the origin of such a difference, we consider first the classical magnetic/non-magnetic multilayers in which the magnetic layers contain FM regions only (most multilayers produced by physical deposition methods exhibit this behaviour). In such cases, the GMR effect arises from spin-dependent scattering originating from electron paths of the type "FM region 1  NM region  FM region 2" and this is the conventional GMR FM term observed in physically deposited multilayers [1][2][3][4][5] which saturates at the above mentioned magnetic fields.…”

Section: A Ferromagnetic and Superparamagnetic Contributions To The mentioning

confidence: 99%

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Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: Origin of the absence of oscillatory behavior

et al. 2009

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─ A detailed study of the evolution of the magnetoresistance was performed on electrodeposited Co/Cu multilayers with Cu layer thicknesses ranging from 0.5 nm to 4.5 nm. For thin Cu layers (up to 1.5 nm), anisotropic magnetoresistance (AMR) was observed whereas multilayers with thicker Cu layers exhibited clear giant magnetoresistance (GMR) behaviour. The GMR magnitude increased up to about 3.5 to 4 nm Cu layer thickness and slightly decreased afterwards. According to magnetic measurements, all samples exhibited ferromagnetic (FM) behaviour. The relative remanence turned out to be about 0.75 for both AMR and GMR type multilayers. This clearly indicates the absence of an antiferromagnetic (AF) coupling between adjacent magnetic layers for Cu layers even above 1.5 nm where the GMR effect occurs. The AMR behaviour at low spacer thicknesses indicates the presence of strong FM coupling (due to, e.g., pin-holes in the spacer and/or areas of the Cu layer where the layer thickness is very small). With increasing spacer thickness, the pin-hole density reduces and/or the layer thickness uniformity improves which both lead to a weakening of the FM coupling. This improvement in multilayer structure quality results in a better separation of magnetic layers and the weaker coupling (or complete absence of interlayer coupling) enables a more random magnetization orientation of adjacent layers, all this leading to an increase of the GMR. Coercive field and zero-field resistivity measurements as well as the results of a structural study reported earlier on the same multilayers provide independent evidence for the microstructural features established here. A critical analysis of former results on electrodeposited Co/Cu multilayers suggests the absence of an oscillating GMR in these systems. It is pointed out that the large GMR reported previously on such Co/Cu multilayers at Cu layer thicknesses around 1 nm can be attributed to the presence of a fairly large superparamagnetic (SPM) fraction rather than being due to a strong AF coupling. In the absence of SPM regions as in the present study, AMR only occurs at low spacer thicknesses due to the dominating FM coupling.

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Section: B Magnetoresistancesupporting

confidence: 57%

Section: A Ferromagnetic and Superparamagnetic Contributions To The mentioning

confidence: 99%

Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: Origin of the absence of oscillatory behavior

et al. 2009

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“…8, in the two series labeled as (1)(2)(3)(4) and (51)(52)(53)(54)(55), the addition of a small amount of Ag + ions to the bath resulted definitely in an improvement of the GMR magnitude. For further additions of Ag + ions to the bath (typically with concentrations above 1%), the GMR magnitude showed an overall decrease down to very small GMR values for the highest Ag + ion concentrations applied.…”

Section: Methodsmentioning

confidence: 98%

“…This can be an explanation for the relatively easy formation of very thin (1 nm or less) and still continuous Cu layers between Co layers in sputtered Co/Cu multilayers, which then enable the development of an oscillatory exchange coupling via the NM spacer and the associated oscillatory GMR. [2][3][4] For other techniques allowing an equilibration of the atoms being deposited, alternative routes are required to achieve a layer-by-layer growth and the formation of better interfaces.…”

Section: D332mentioning

confidence: 99%

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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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CoCu

Note¹

2022

Magnetic Properties of Metals: Magnetic and Electric Properties of Magnetic Metallic Multilayers

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Giant magnetoresistance and interlayer exchange coupling in Ni-Co/Cu multilayer films

Cited by 46 publications

References 23 publications

Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: Origin of the absence of oscillatory behavior

Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: Origin of the absence of oscillatory behavior

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

CoCu

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