Magnetron Co-sputtering Deposition Research Articles

Super-hard and well-tough (TiZrVCrCoNi)Nx high entropy nitride coatings with biphasic nanocomposite structure

High entropy nitride (HEN) coating is a new choice to replace traditional nitride as a protective coating. Through rational composition design, (TiZrVCrCoNi)Nx HEN coatings under different N2 gas flow rates (RN) were fabricated by multi-target magnetron co-sputtering deposition. The increasing RN enhanced N content in the HEN coatings, which influences the structural, mechanical, and corrosion characteristics of the coatings. The increase of N content caused the phase structure to transform from an amorphous phase to a face-centered-cubic (FCC) phase in the coatings. At a high N content of 47.7 at.% (RN = 15 sccm), the coating with a biphasic nanocomposite structure exhibits a high-quality combination of super-hardness, good toughness, anti-friction property, and excellent corrosion resistance. While the hardness can reach the super-hard level (40.9 ± 0.75 GPa), the toughness is not decreased much (3.35 ± 0.08 MPa m1/2). Besides, the corrosion current density of it (1.86 × 10−8 A/cm2) is nearly two orders of magnitude lower than 304 stainless steel (1.24 × 10−6 A/cm2). Therefore, (TiZrVCrCoNi)Nx HEN coatings present outstanding mechanical properties and corrosion resistance, which have potential applications in various fields.

Enhancing SiGeSn nanocrystals SWIR photosensing by high passivation in nanocrystalline HfO2 matrix

SiGeSn nanocrystals (NCs) in oxides are of considerable interest for photo-effect applications due to the fine-tuning of the optical bandgap by quantum confinement in NCs. We present a detailed study regarding the silicon germanium tin (SiGeSn) NCs embedded in a nanocrystalline hafnium oxide (HfO2) matrix fabricated by using magnetron co-sputtering deposition at room temperature and rapid thermal annealing (RTA). The NCs were formed at temperatures in the range of 500–800 °C. RTA was performed to obtain SiGeSn NCs with surfaces passivated by the embedding HfO2 matrix. The formation of NCs and β-Sn segregation were discussed in relation to the deposition and processing conditions by employing HRTEM, XRD and Raman spectroscopy studies. The spectral photosensitivity exhibited up to 2000 nm in short-wavelength infrared (SWIR) depending on the Sn composition was obtained. Comparing to similar results on GeSn NCs in SiO2 matrix, the addition of Si offers a better thermal stability of SiGeSn NCs, while the use of HfO2 matrix results in better passivation of NCs increasing the SWIR photosensitivity at room temperature. These results suggest that SiGeSn NCs embedded in an HfO2 matrix are a promising material for SWIR optoelectronic devices.

High thermoelectric performance of aluminum-doped cuprous selenide thin films with exceptional flexibility for wearable applications

Flexible thin-film generators are a great promising energy source for wearable device applications. In this work, Al-doped Cu2Se thin film with highly (0l0) preferred orientation was achieved by magnetron co-sputtering deposition. It possessed a high ZT value of 0.76 at 275 °C, and further surface organic component coating treatment resulted in its exceptional flexibility. The Al dopant was proven to be successfully introduced into the lattice of Cu2Se samples, which can decrease carrier concentration and result in the enhancement of Seebeck coefficient. Meanwhile, a significant decline in lattice thermal conductivity was achieved after Al doping. The organic component coating can prevent the fracture of inorganic thin films after bending. The resistance difference (∆R/R0) after 1000 cycles of bending was lower than 10%, which is a great improvement compared with that in pristine thin film (over 15%). The thermoelectric device prepared by the Al-doped Cu2Se obtained a stable power density of ∼5.7 W m−2 at a temperature difference of 20 °C.

Bamboo-like dual-phase nanostructured copper composite strengthened by amorphous boron framework

Grain boundary engineering is a versatile tool for strengthening materials by tuning the composition and bonding structure at the interface of neighboring crystallites, and this method holds special significance for materials composed of small nanograins where the ultimate strength is dominated by grain boundary instead of dislocation motion. Here, we report a large strengthening of a nanocolumnar copper film that comprises columnar nanograins embedded in a bamboo-like boron framework synthesized by magnetron sputtering co-deposition, reaching the high nanoindentation hardness of 10.8 GPa among copper alloys. The boron framework surrounding copper nanograins stabilizes and strengthens the nanocolumnar copper film under indentation, benefiting from the high strength of the amorphous boron framework and the constrained deformation of copper nanocolumns confined by the boron grain boundary. These findings open a new avenue for strengthening metals via construction of dual-phase nanocomposites comprising metal nanograins embedded in a strong and confining light-element grain boundary framework.

The microstructure and hardness of Cu-76 at.% Ag multilayers prepared by co-deposition

In this paper, the Cu-76 at.% Ag multilayers without a diffusion barrier component were prepared by magnetron sputtering co-deposition. The Cu–Ag multilayers are composed of sublayers whose composition changes continuously and regularly. The hardness of co-deposited multilayers is higher than that of mixed monolayer with similar average grain size, due to the component fluctuations along the direction of membrane growth hindering dislocation movement. When the compositional modulation period is reduced from 110 nm to 11 nm, the nanoindentation hardness of co-deposited multilayers increases by 41.3% from 2.35 GPa to 3.32 GPa. Compared with the sequential-deposited multilayers with the same composition, the hardness of co-deposited multilayers is lower than that of sequential-deposited multilayers during small modulation period (λ = 11, 22 nm). At small modulation periods, the contribution of compositional gradient to hardness in co-deposited multilayers is lower than that of interface strengthening in sequential-deposited multilayers, which is attributed to the higher interfacial coherence of the co-deposited multilayers. This study proposes a novel multilayers without diffusion barrier element, further elucidate the strengthening mechanism of hardness, enriching the research of binary co-deposited multilayers material systems.

Structure evolution and mechanical properties of Al-alloyed tantalum diboride films prepared by magnetron sputtering co-deposition

Alloying of transition metal diborides with other metals seems to be a suitable way to maintain their excellent mechanical properties under high-temperature loads. Here, we focus on the perspective tantalum diboride (TaB2) hard film, where we investigate the effect of aluminum alloying on the thermally induced structural evolution and mechanical properties of α-Ta1−xAlxB2 using a combination of density functional theory and experiments. Ab initio calculations predict a strong tendency toward the spinodal phase decomposition of the α-TaAlB2 solid solution into isostructural binaries in the entire concentration range at T = 0 K. However, an increase in temperature (T > 773 K) leads to stabilization of the α-Ta1−xAlxB2 solid solution at x < 0.5. The experimental results of magnetron co-sputtered Ta0.75Al0.25B2.14 and Ta0.69Al0.31B2.16 films with aluminum concentrations of 8 and 12.5 at. %, respectively, confirm the insolubility of aluminum in the TaB2 phase. The structure has a nanocomposite character formed by α-TaB2 nanofilaments surrounded by an Al-rich tissue phase. The films are structurally stable up to 1200 °C, but Al atoms already begin to diffuse from the boundary regions when the temperature exceeds 1000 °C. Al alloying causes a decrease in hardness, since the hardness of the reference as-deposited TaB1.21, Ta0.75Al0.25B2.14, and Ta0.69Al0.31B2.16 films is 34, 28, and 27 GPa, respectively. Exposing the films to high temperatures does not lead to a hardening effect; the hardness of Al-depleted films annealed at a temperature of 1200 °C decreased by approximately 10%. The decrease in Young's modulus from 420 GPa (TaB1.21) to 370 GPa (Ta0.69Al0.31B2.16) indicates a tendency toward the ductile behavior of Al alloyed films under mechanical load.

Revealing the effects of Nb micro-alloying on microstructure and mechanical properties of FeCrAl thin films: Experimental and computational investigations

FeCrAl-based materials have attracted ever-increasing attentions due to their excellent resistances against high-temperature oxidation and stress-corrosion cracking, while enhancement of their mechanical properties can expand their potential applications. In this work, the micro-alloying method by adding Nb was applied to enhance the mechanical property of FeCrAl. The FeCrAl thin films with different Nb contents (Fe-16Cr-5Al, Fe-14Cr-5Al-1Nb, Fe-12Cr-5Al-2Nb, Fe-13Cr-3Al-7Nb, in wt%) were synthesized using magnetron co-sputter deposition. Benefiting from the refined grain size, the as-deposited Fe-13Cr-3Al-7Nb thin film exhibited the highest hardness (3.3 GPa), followed by Fe-14Cr-5Al-1Nb (1.5 GPa) and Fe-12Cr-5Al-2Nb (1.2 GPa), whereas the hardness of Nb-free film was the lowest (0.8 GPa). The fracture resistance (which is related to the ratio of hardness and elastic modulus) also enhances with the addition of Nb. After annealing (873 K for 6 h), the hardness of the Fe-13Cr-3Al-7Nb thin film further increased to ~6.7 GPa, in contrast to the as-annealed Nb-free thin film with no obvious hardness change. The CALPHAD (CALculation of PHAse Diagram) results indicate that with adding Nb the original single BCC (body centered cubic) phase tended to decompose into the Fe-rich and Cr-rich BCC domains, which is consistent with the transmission electron microscopic (TEM) observations. The observed strengthening of the annealed Nb-containing samples is therefore attributed to the phase separation. The first-principles calculations also support this notion. Thus, the current work has delineated the effect of Nb addition on both deposited and annealed FeCrAl-based thin films, which shows the usefulness of combined experimental and computational methods in interpreting microstructure and mechanical property evolutions of engineering materials.

Multiple Exciton Generation in 3D-Ordered Networks of Ge Quantum Wires in Alumina Matrix.

Thin films containing 3D-ordered semiconductor quantum wires offer a great tool to improve the properties of photosensitive devices. In the present work, we investigate the photo-generated current in thin films consisting of an interconnected 3D-ordered network of Ge quantum wires in an alumina matrix. The films are prepared using nitrogen-assisted magnetron sputtering co-deposition of Ge and Al2O3. We demonstrate a strong photocurrent generation in the films, much stronger than in similar films containing Ge quantum dots. The enhanced photocurrent generation is the consequence of the multiple exciton generation and the films’ specific structure that allows for efficient carrier transport. Thin film with the largest nitrogen content showed enhanced performance compared to other thin films with 1.6 excitons created after absorption of a single photon at an energy nearly equal to the double bandgap value. The bandgap value depends on the geometrical properties of the quantum wires, and it is close to the maximum of the solar irradiance in this case. In addition, we show that the multiple exciton generation is the most pronounced at the photon energy values equal to multiple values of the thin film bandgap.

Microstructures, Mechanical Behavior, and Radiation Damage of (TiVCr)x-(TaW)1-x Binary System High-Entropy Alloy Films

An experimental method for preparing high-entropy thin films with gradient changes of alloying elements by magnetron sputtering co-deposition is proposed in this work to evaluate the effect of alloying element composition changes on the properties of non-equal molar ratio high-entropy alloys. The (TiVCr)x-(TaW)1-x binary system thin films were deposited by a magnetron sputtering system with two intermediate alloy targets. The surface morphology, element composition, roughness, and phase structure of the coatings were studied with scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffractometer (XRD), atomic force microscope (AFM), and transmission electron microscope (TEM). The results show that at x = 0.51, the films had the best mechanical properties under the action of multiple strengthening mechanisms, and the hardness and modulus reached 27.61 GPa and 274.42 GPa, respectively. Due to higher hardness and special surface morphology, the films showed a lower average friction coefficient and had excellent wear resistance with wear rates of 0.34 and 5.01 × 10−9 mm3/(N·mm), respectively. On the other hand, it was found that forming a BCC polycrystalline structure and an amorphous-mixed structure can improve the radiation resistance of the material.

Layered structure enhances the hardness of Cu-48at.%Cr film prepared by co-sputtering deposition technique

The Cu-48at.%Cr film was prepared by magnetron co-sputtering deposition technique with working pressure from 0.2 Pa to 1.5 Pa. The microstructure and nanoindentation hardness were investigated. When the working pressure decreased to 0.2 Pa, the consecutive layered structure formed. The formation of layered structure was attributed to the diffusion barrier ability of Cr element and the uphill diffusion of Cu atoms. While at higher working pressure, the sputtering particles energy near the substrate was not enough to promote the Cu diffusion. Therefore, the layered structure became indistinct as the working pressure increased. Owing to the interface strengthen, this layered structure made the nanoindentation hardness increase markedly from 4.2 GPa to 9.3 GPa as the working pressure decreased from 1.5 Pa to 0.2 Pa. This study could provide a good basis for preparing the film with specific microstructure in Cu–Cr system, even in other immiscible systems.

Thermal stability of co-sputtered TaCu amorphous nano-multilayers

Comprehensive knowledge of the thermal stability of films is essential from the perspective of design and application. In this case, TaCu amorphous nano-multilayers with a Ta nominal content of 68 at.% were prepared by magnetron co-sputtering deposition technique. Nano-multilayers with a modulation period of 12.8 nm are constituted of equal-thickness sublayers both exhibiting pronounced Ta-rich amorphous phase. The Ta content presents an obviously sinusoidal fluctuation along the growth direction. The relatively intuitive processes of phase separation and layered structure destruction were obtained through isothermal annealing in the temperature range of 450–700 ℃ for 1 h. The high interfacial energy produced by co-sputtering deposition drives the thermally-activated Cu atoms to diffuse uphill, leading to the amorphous sublayers with the higher Cu content crystallizing initially at 450 ℃. Upon annealing at 480 ℃ for 1 h, the formation of the thermal groove between adjacent Cu grains and the diffusion of Ta atoms along the Cu grain boundaries synergistically induce the sublayers to fracture. Nanoindentation experiments showed that the hardness of the annealed films increases due to the clearer interface by uphill diffusion, but the enhancement only remains until the layered structure disappears. This study provides a good basis for the design and application of TaCu amorphous nano-multilayers, even in other immiscible systems.

Electrical and optical properties of electrochromic device with WO3:Mo film prepared by RF magnetron Co-Sputtering

In this work, we investigate the electrical and optical properties of an electrochromic device (ECD) that has molybdenum-doped tungsten trioxide (WO 3 :Mo) electrode. Also, it's surface morphology, coloration efficiency and light transmittance are evaluated. To fabricate the ECD, the WO 3 :Mo film as the working electrode and the Nickel oxide (NiO) film as the counter electrode are prepared by RF magnetron co-sputtering deposition respectively. WO 3 and Mo are set as targets and fluorine-doped tin oxide (FTO) glass, size 2 × 2 cm, is prepared as a substrate. Both targets are sputtered under the same sputtering conditions such as gas pressure, target distance and rotational speed of substrate at 15 mTorr, 5 cm and 5 rpm, respectively. In the co-sputtering process, all conditions were the same for the WO 3 target and Mo target, but only the RF power applied to each target was changed. The RF power applied to the WO 3 target was fixed at 150 W, while the RF power to the Mo target was increased from 50 W to 250 W in 100 W increments giving a difference in dopant concentrations. At the RF power to the Mo target of 50 W, 150 W, and 250 W, respectively, the coloration efficiency of the ECDs was 67.58 cm 2 C −1 , 40.60 cm 2 C −1 , 36.89 cm 2 C −1 . The optimum RF power to the Mo target for the fabrication of an WO 3 :Mo film for use as an electrode in ECD was 50 W at the fixed 150 W RF power to the WO 3 target, and the fabricated films showed an amorphous structure and the highest coloration efficiency. The transmittances of the prepared ECD were 64.63% and 17.17%, respectively, in the bleaching and coloring state. • RF Magnetron co-sputtering was used for fabricate the WO 3 :Mo thin film for made the electrochromic devices. • The concentration ratio was adjusted by varies the RF power applied to Mo target. • The optimal parameter was obtained from RF power was 150 W to WO 3 target and 50 W to Mo target. • The CE of the ECD with WO 3 :Mo electrode were increased to 67.58 cm 2 ·C -1 compare to undoped WO 3 electrode 41.45cm 2 ·C -1 .

Influence of the power density and working pressure in the magnetron co-sputtering deposition of ZnO–SnO2 thin films and their effect in photocatalytic hydrogen production

This work presents the photocatalytic hydrogen production of ZnO–SnO2 thin films deposited by the magnetron co-sputtering technique varying the deposit conditions as power density and working pressure. As the power density of Sn increase, it was observed an increase in the presence of the SnO2 orthorhombic phase. Because of this increase, the number of defects generated in the films increases as it was corroborated by PL and XRD results. On the other hand, when the films were deposited at different working pressures, more significant optical and physicochemical changes were observed. The XRD results could be verified revealed that the working pressure could control the preferential orientation of the ZnO phase in the films. The working pressure also influenced the presence of two different SnO2 phases (orthorhombic and tetragonal). The surface roughness is also affected by the various working pressures since it increased when the deposits were made at low working pressures. The decrease in the roughness affects the transmittance percentage of the films, decreasing these to affecting the pass of the visible light. The photocatalytic efficiency was influenced by different structural defects that can act as electron traps or recombination centers.

New type Schottky diodes based on the heterostructure of transition metal oxides: p-La2/3Sr1/3VO3/n-TiO2

We make a new type of bipolar Schottky diodes using the p-type La2/3Sr1/3VO3 (LSVO)/n-TiO2 heterostructure. The p-type LSVO metal thin films are grown on various substrates using radio frequency magnetron co-sputtering deposition. We find that the LSVO film grown on anatase TiO2 layer produce the lowest resistivity of 0.28 mΩ cm. We discover that the resistivity decreases with decreasing LSVO film thickness for LSVO/TiO2/Si structures. Hall measurements are performed and the dielectric functions of LSVO films are measured. The effective mass of LSVO/TiO2/Si is determined to be 2.54 ± 0.05 m0. The current-voltage curves of the Schottky diodes of p-LSVO/n-TiO2 is measured and is explained using band alignment diagram. We identify a new type of Schottky diode, where both electrons in n-TiO2 and holes in p-LSVO can flow under bias.

Effects of Mg addition on the phase formation, morphology, and mechanical and tribological properties of Ti-Nb-Mg immiscible alloy coatings produced by magnetron co-sputtering

The addition of Mg to Ti-based alloys is a promising method for improving bioactivity in this type of alloys because Mg is absorbed by the body and can biologically activate the implant material, facilitating its adaptation. However, the fabrication of Ti-Nb-Mg alloys by conventional processes is extremely difficult due to the very low solubility of Mg in Ti and the very large difference in their melting points. Therefore, non-equilibrium processing methods such as magnetron sputtering can be used to produce metastable supersaturated Ti-Mg alloys with low density and attractive mechanical properties. In the present study, Ti85-xNb15Mgx (x = 5, 8, 16, 25 at.%) coatings were successfully produced by magnetron co-sputtering deposition on AISI 316L SS substrates. The effects of Mg content on the phase formation, morphology, and mechanical and tribological properties of the Ti-Nb-Mg coatings were investigated. The coatings with lower Mg contents (5 and 8 at.%) presented a predominance of the α (hexagonal close packed - HCP) phase (near α-Ti), the coating with 16 at.% Mg had near equal relative quantity of the α and the β phases (α + β type), and the coating with 25 at.% Mg had almost only the β phase (β-Ti type). A greater stabilization of the β-Ti phase with the increase of Mg content yielded a decrease in both the elastic modulus (102 to 88 GPa) and the hardness values (2.7 to 2.1 GPa). Tribological tests did not detect any detachment of the coatings, due to the high plastic joint strain of the coating/substrate systems, that ensures integrity and good adhesion. Failure was observed only on the coating and depended on α and β relative amounts in the coating.

Indium silicon oxide thin films for infrared metaphotonics

We demonstrate silicon-doped indium oxide (ISO) with tunable epsilon near-zero and plasmonic behavior and propose it as a Si-compatible alternative material for metaphotonic applications in the mid-infrared (MIR) spectral range. ISO thin films were grown using DC and RF magnetron cosputtering deposition. Post-deposition thermal annealing was performed that resulted in large tunability of the optical dispersion data, as measured directly by variable-angle ellipsometry. Screened plasma wavelengths in the range 1.7 μm–5.8 μm were experimentally obtained depending on the annealing conditions. Moreover, ISO films with 350 nm thickness were investigated by atomic force microscopy that reveals a maximum rms roughness of 1.9 nm, enabling high-quality nanofabrication. In order to demonstrate the suitability of ISO thin films for the fabrication of plasmonic structures, we have produced ISO nanoparticle disk arrays using electron-beam lithography on Al2O3 substrates and shown, using both finite element method simulations and Fourier transform infrared spectroscopy, distinctive plasmonic resonances at MIR wavelengths tuned by the nanoparticles' spacing and aspect ratio. A figure of merit based on Mie theory is computed for spheres whose radii are either λ/10 or λ/3 over a broad spectral range that enables quantitative comparison with alternative plasmonic materials and reveals the full potential of ISO for engineering localized surface plasmons across the MIR spectral range. The development of fully Si-compatible plasmonic materials with engineered optical dispersion is important to enable cost-effective photonic-plasmonic high-density device integration for metaphotonic research.

Electronic Effects Determine the Selectivity of Planar Au-Cu Bimetallic Thin Films for Electrochemical CO2 Reduction.

Au–Cu bimetallic thin films with controlled composition were fabricated by magnetron sputtering co-deposition, and their performance for the electrocatalytic reduction of CO2 was investigated. The uniform planar morphology served as a platform to evaluate the electronic effect isolated from morphological effects while minimizing geometric contributions. The catalytic selectivity and activity of Au–Cu alloys was found to be correlated with the variation of electronic structure that was varied with tunable composition. Notably, the d-band center gradually shifted away from the Fermi level with increasing Au atomic ratio, leading to a weakened binding energy of *CO, which is consistent with low CO coverage observed in CO stripping experiments. The decrease in the *CO binding strength results in the enhanced catalytic activity for CO formation with the increase in Au content. In addition, it was observed that copper oxide/hydroxide species are less stable on Au–Cu surfaces compared to those on the pure Cu surface, where the surface oxophilicity could be critical to tuning the binding strength of *OCHO. These results imply that the altered electronic structure could explain the decreased formation of HCOO– on the Au–Cu alloys. In general, the formation of CO and HCOO– as main CO2 reduction products on planar Au–Cu alloys followed the shift of the d-band center, which indicates that the electronic effect is the major governing factor for the electrocatalytic activity of CO2 reduction on Au–Cu bimetallic thin films.

Effects of Hf buffer layer at the Y-doped HfO2/Si interface on ferroelectric characteristics of Y-doped HfO2 films formed by reactive sputtering

10 nm-thick ferroelectric (FE) HfO2 films with 1.5 mol% yttrium-doping were fabricated by mid-frequency reactive magnetron co-sputtering deposition on bare Si and underlying metal Hf. Yttrium was incorporated into the HfO2 layers by simultaneously sputtering from Y and Hf metal targets under oxygen atmosphere. The effects of interfacial layer on structural and electrical properties of Y:HfO2 films have been systemically studied using high-resolution transmission electron microscopy (TEM), X-ray diffraction (XRD) and electrical measurements. Based on TEM and XRD measurements, the presence of a non-centrosymmetric orthorhombic phase which is responsible for ferroelectricity in yttrium-doped HfO2 (Y:HfO2) films could be detected. As an initial protective layer, the ultra-thin metal Hf (~1 nm) layer covers the silicon surface and prevents the native oxide growth during the deposition and post-annealing process. Results reveal that the thickness of interfacial layer is significantly reduced by deposit a Hf buffer layer and a remanent polarization Pr of up to 14 μC/cm2 can be detected in P-V measurement. The strategy of using Hf buffer layer to improve electrical properties of HfO2 film is a feasible method for the fabrication of metal-insulator-semiconductor (MIS) capacitor based on FE-HfO2/Si gate stack.

A multifunctional vanadium-doped cobalt oxide layer on silicon photoanodes for efficient and stable photoelectrochemical water oxidation

p+n junction Si cells with V doped Co oxide were fabricated via magnetron co-sputtering deposition as photoanodes for efficient OER performance.

Local structure and X-ray magnetic circular dichroism of Au in Au-Co nanoalloys

Coupling a plasmonic metal with a magnetic one in thin films and nanostructures is very interesting for the emerging field of magnetoplasmonics. In particular, coupling through alloying is a promising strategy to induce a magnetic moment on the plasmonic metal atoms, in a way that is intimately related to the local structure of the (metastable) alloy material. In this framework, Au:Co bimetallic films have been produced via magnetron co-sputtering deposition. X-ray absorption spectroscopy (XAS) at both Au- and Co-edges clearly indicates the formation of a full-metallic layer composed for the major part of a binary AuxCo1−x alloy, with x = 0.7–0.8. XAS and transmission electron microscopy analyses suggest the presence of a minor fraction of segregated metals. X-ray magnetic circular dichroism (XMCD) analysis at Au L2,3 edges detected a net magnetic moment of Au atoms (μ = 0.06 μB), significantly larger (≈3.5 times) that the one for Au-capped Co nanoclusters and comparable to the one for a Co-rich Au/Co multilayer, despite the 4 times larger concentration of Co with respect to the present case. This Au-Co magnetic coupling is favored by a high degree of mixing of the two metals in the alloy.