Precipitation of nanoscale Co particles in a granular Cu–Co alloy with giant magnetoresistance

Yanga, G.Y.; Zhu, Jing; Wang, W.D.; Zhang, Z.; Zhu, Fangyuan

doi:10.1016/s0025-5408(00)00283-x

Cited by 16 publications

(6 citation statements)

References 13 publications

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“…A similar result was obtained in Cu 85 Co 15 granular alloys 47 and observed by HRTEM in heterogeneous Cu 88 Co 12 ribbons prepared by melt-spinning. 48 In fact, our results are different from what was usually observed for Cu-Co alloy thin films or nanowires obtained by electrodeposition. 47,49 In these cases, the analysis of the XRD pattern shows that copper and cobalt form a solid solution with a cell parameter that follows the Vegard's law.…”

Section: B Crystalline Structurecontrasting

confidence: 99%

Atomic-scale investigation and magnetic properties of Cu80Co20 nanowires

Hannour

Lardé

Jean

et al. 2011

Journal of Applied Physics

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Articles you may be interested inMagnetic behavior of NiCu nanowire arrays: Compositional, geometry and temperature dependence J. Appl. Phys. 116, 033908 (2014); 10.1063/1.4890358Post magnetic field annealing effect on magnetic and structural properties of Co80Pt20 nanowires and nanotubes fabricated by electrochemical method J. Appl. Phys. 115, 17A762 (2014); 10.1063/1.4868179Structural and magnetic characterization of as-prepared and annealed FeCoCu nanowire arrays in ordered anodic aluminum oxide templates Cu 80 Co 20 granular alloy nanowires were synthesized by electrodeposition method and investigated by x-ray diffraction (XRD), Laser Assisted Wide Angle Tomographic Atom Probe (LAWATAP), and SQUID magnetometry. XRD results reveal the existence of a fcc Cu matrix and fcc Co-rich nanograins, with a preferred orientation along the [200] direction (perpendicular to the substrate surface). The Co-rich nanograins could be coherent with the Cu matrix. 3D reconstructions of a nano-sized volume, obtained by LAWATAP, reveal the heterogeneous aspect of the Cu 80 Co 20 nanowires: Co-rich nanoclusters with size between 2 and 10 nm are detected, and the presence of Cu and Co oxides is evidenced. Magnetization measurements indicate that the Co-rich nanoclusters are superparamagnetic, with a blocking temperature that extends up to, at least, room temperature. The presence of ferromagnetic domains at room temperature indicates that some Co-rich nanoclusters are correlated within a volume that corresponds to a so-called interacting superparamagnetic phase. As a matter of fact, by LAWATAP atomic-scale analysis, a very good correlation is obtained between microstructure and magnetic properties.

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Section: B Crystalline Structurecontrasting

confidence: 99%

Atomic-scale investigation and magnetic properties of Cu80Co20 nanowires

Hannour

Lardé

Jean

et al. 2011

Journal of Applied Physics

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“…Core–shell nanoparticles of Cu–Co appeared to form a regular arrangement of particles (part a of Figure ), which may be due to magnetic interaction between the particles. Yang et al have earlier reported nanoscale Cu 88 Co 12 alloy particles with an average size of ∼10 nm from arc melting, whereas nanorods of Cu 90 Co 10 alloy (diameter = 200 nm, length = 5 μm) have been reported by electrochemical deposition method using polycarbonate membrane as a template . Hydrazine hydrate works as good reducing agent under alkaline conditions as shown by the following reactions: 2 Cu 2 + + normalN 2 normalH 4 . normalH 2 normalO + 4 OH − → 2 Cu + normalN 2 + 5 normalH 2 normalO 2 Co 2 + + normalN 2 normalH 4 . normalH 2 normalO + 4 OH − → 2 Co + normalN 2 + 5 normalH 2 normalO …”

Section: Resultsmentioning

confidence: 99%

“…Nanoscale particles of metals, alloys, and core–shell structures have attracted much attention due to their unique electronic, optical, biological, catalytic, and magnetic properties. − Metallic and bimetallic nanoparticles have applications in drug delivery, in hyperthermia, as electrocatalysts, and in magnetic devices. − Cu–Co alloy particles show giant magnetoresistance (GMR) behavior originating mainly from spin-dependent scattering of conduction electrons at the interface of the ferromagnetic particles. − The microstructural factors controlling GMR effect in granular materials are mainly the size distribution and the volume fraction of the ferromagnetic Co particles embedded in the nonferromagnetic matrix as well as the roughness of the interfaces . Ferromagnetic behavior was observed in cobalt-rich bulk Cu x Co 100– x systems ( x = 20–100) at room temperature while the Cu 90 Co 10 system showed paramagnetic behavior .…”

Section: Introductionmentioning

confidence: 99%

“…A number of physical techniques have been used to produce metastable solid solutions of Cu–Co such as arc melting, , mechanical alloying, electrochemical deposition, melt-spinning method, − and ball milling, which show limited solubility of Cu and Co. The copper–cobalt binary system is an immiscible system (no solubility of Cu in Co or Co in Cu) under ambient conditions.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Electrocatalytic Activity of Copper–Cobalt Nanostructures

et al. 2011

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Novel core–shell nanostructures containing Cu and Co have been synthesized using the microemulsion method at 700 °C. The core consists of Cu–Co composite particles, whereas the shell is composed of Cu–Co alloy particles (shell thickness ∼12 nm). It is to be noted that in bulk Cu–Co binary system there is practically no miscibility. TEM studies show formation of spherical-shaped nanoparticles of core–shell structures. The composition of the core (Cu–Co composite) and shell (Cu–Co alloy) were confirmed by XPS studies. The formation of the Cu–Co alloy as the shell is mainly driven by surface energy considerations. We have also obtained Cu–Co nanocomposites (by controlling the concentration of reducing agent) with particle size in the range of 40–200 nm. These Cu–Co nanostructures show ferromagnetic behavior at 4 K. The saturation magnetization of the core–shell (Cu–Co composite @ Cu–Co alloy) nanostructure (125 emu/g) is found to be higher than that of pure Cu–Co nanocomposite or alloy, which may be useful for applications as a soft magnet. Electrochemical studies of these nanocrystalline Cu–Co particles show higher hydrogen evolution efficiencies (∼5 times) compared to bulk (micrometer-sized) Cu–Co alloy particles.

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“…Granular Cu–Co alloys can be obtained by vapor quenching, sputtering, ,− melt spinning, − molecular beam epitaxy, chemical deposition, electrodeposition, − pulse laser ablation, , rolling method, or mechanical alloying. − In this work, we have prepared Cu 80 Co 20 alloys with high-energy ball milling under ambient atmosphere conditions. We found that, after 20 h of milling, the powder exhibits at 5 K a positive magnetoresistance of 0.8% under low magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Atomic Scale Characterization and Magneto-Transport Properties of Mechanically Milled Cu–Co Type Alloys

et al. 2012

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We have prepared Cu 80 Co 20 powders by high-energy ball milling under ambient atmosphere. The evolutions of both the microstructure and the magnetic properties have been investigated as a function of milling time. 3D-focused ion beam was used for microstructural characterization for low milling time (1.5 h). For higher milling time (20 h) atom probe tomography was used to investigate at the atomic scale the elemental distribution of chemical species. In the first steps of milling, the powder presents a ferromagnetic signal due to the presence of micrometric cobalt particles. After 20 h of milling, the powder is composed of CoO particles with diameter around 10−50 nm surrounded by a copper rich matrix (Cu-84 ± 2%, Co-16 ± 2%) and a few cobalt-rich nanoclusters. For this milling time, a typical giant magnetoresistive effect is observed. A positive magnetoresistive effect is also observed at 5 K under low magnetic fields, which is related to the presence of Co oxides clusters. After a heat treatment at 450°C for 1 h, the precipitation of Co into the copper rich matrix is observed, the giant magnetoresistive effect is enhanced, and the positive magnetoresistive effect disappears.

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Precipitation of nanoscale Co particles in a granular Cu–Co alloy with giant magnetoresistance

Cited by 16 publications

References 13 publications

Atomic-scale investigation and magnetic properties of Cu80Co20 nanowires

Atomic-scale investigation and magnetic properties of Cu80Co20 nanowires

Enhanced Electrocatalytic Activity of Copper–Cobalt Nanostructures

Atomic Scale Characterization and Magneto-Transport Properties of Mechanically Milled Cu–Co Type Alloys

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