Surfactant-Mediated Modification of the Magnetic Properties of Co<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>/</mml:mi></mml:math>Cu(111) Thin Films and Superlattices

Camarero, Julio; Graf, Thomas; Miguel, J. J. de; Miranda, Rodolfo; Kuch, W.; Zharnikov, Michael; Dittschar, A.; Schneider, Claus M.; Kirschner, J.

doi:10.1103/physrevlett.76.4428

Cited by 109 publications

(51 citation statements)

References 16 publications

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“…In the case of MBE-grown Co/Cu multilayers, the use of Pb as surfactant could be demonstrated to yield continuous Cu layers down to 3 monolayer coverage 18 and such Co/Cu multilayers have, indeed, exhibited a strong AF coupling. 21 In the application of a surfactant element for the growth of a Co/Cu multilayer, 20 one monolayer of the surfactant atoms is deposited first on the substrate. The surfactant atoms, due to their high mobility and low surface energy, will then climb up on top of the multilayer and build a kind of floating sheet.…”

Section: D332mentioning

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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Section: D332mentioning

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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“…Because we discussed here examples from metal homoepitaxy, we would like to point out the work using Pb for Cu (111) homoepitaxy [281,282]. For surfactants in metal heteroepitaxy, we refer to Refs [278,283], and for their use in semiconductors, we refer to the review [270].…”

Section: Surfactantsmentioning

confidence: 99%

Epitaxial Growth of Thin Films

Brune

2014

Surface and Interface Science

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This chapter gives an introduction to the epitaxial growth of thin films on solid substrates. The term epitaxy refers to the growth of a crystalline layer on (epi) the surface of a crystalline substrate, where the crystallographic orientation of the substrate surface imposes a crystalline order (taxis) onto the thin film. This implies that film elements can be grown, up to a certain thickness, in crystal structures differing from their bulk. If film and substrate have the same crystal lattices, but different lattice constants, the film will be under strain, that is, it will have a slightly different lattice constant than in its own bulk. Both effects, together with the electronic hybridization at the interface, lead to novel properties.One distinguishes homo-and heteroexpitaxy, where the former refers to the growth on one element on a crystal surface of its own and the latter refers to the more general case, where film and substrate materials are different. Note that the first distinguishes itself from crystal growth, as we will see in more detail later.We start this chapter by giving examples from technology, illustrating where thin epitaxial films are used and outlining potential applications that become reality once we are able to grow the respective thin film sequences. We then contrast thin film and crystal growth, respectively, with kinetics and thermodynamics of growth. We introduce the deposition techniques used in epitaxial thin film growth and then discuss the classical thermodynamic approach, which led to the definition of the growth modes. These modes refer to the morphology taken on by a system grown close to thermodynamic equilibrium. Often films are grown far away from equilibrium and their morphology is determined by kinetics, that is, it is the result of the microscopic path taken by the system during growth. This path is determined by the hierarchy of rates of the single atom, cluster or molecular precursor displacements as compared to the deposition rate. Owing to the importance of kinetics, we focus in the rest of the chapter on the kinetic description of growth. In order to simplify the topic, we start with coverages below one atomic layer that is referred to as a monolayer. The first submonolayer part will be on nucleation, followed by a discussion of island shapes that, very much like snowflakes, tell us about the elementary processes that took place during their formation. We then discuss island coarsening, either by evaporation of atoms from their edges, referred to as the Ostwald ripening, or by the diffusion and subsequent coalescence of entire islands, referred to as the

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“…The importance of the use of surfactant elements such as, e.g., Pb, Ag, Bi, Au and In is that their presence on the substrate during layer formation can efficiently promote layer-by-layer growth since they can alter the kinetics of the deposition of adatoms and their incorporation into the existing metal lattice, as well as the surface energy of the growing deposit [1][2][3]. The use of Pb as surfactant was found to have a particularly profound effect on the layer quality of Co/Cu multilayers [2,4,5], leading to a virtually nucleation-free growth and even layer thicknesses. The improved layer quality concomitantly resulted in better physical properties such as stronger antiferromagnetic coupling and higher giant magnetoresistance (GMR) [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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

Fesharaki¹,

Neuróhr²,

Péter³

et al. 2016

J. Electrochem. Soc.

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-In an effort to see the possible surfactant effect of Pb on the formation of electrodeposited multilayers, Co/Cu(Pb) 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 Pb 2 + ions in the solution. The composition analysis by energy dispersive X-ray spectroscopy revealed that the Pb mole fraction in the deposit varies in a non-monotonous manner with Pb 2+ ion concentration. By fitting the measured X-ray diffraction patterns, superlattice satellites could be identified in some of these multilayers. A ferromagnetic-type GMR behavior was observed for Co/Cu(Pb) deposits prepared from baths with small Pb 2+ ion concentration, corresponding to the formation of a layered structure. The GMR magnitude decreased from 8 to 10 % with increasing Pb concentration and, also, changed to a superparamagnetic-type GMR; finally, for high Pb 2+ ion concentrations, the magnetoresistance behavior turned over to anisotropic magnetoresistance characteristic of bulk materials.

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Surfactant-Mediated Modification of the Magnetic Properties of Co/Cu(111) Thin Films and Superlattices

Cited by 109 publications

References 16 publications

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

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

Epitaxial Growth of Thin Films

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

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