Magnetism of cluster-deposited Y–Co nanoparticles

Balamurugan, B.; Skomski, Ralph; Li, X. Z.; Shah, Vaishali; Hadjipanayis, G. C.; Shield, Jeffrey E.; Sellmyer, David J.

doi:10.1063/1.3549602

Cited by 9 publications

(4 citation statements)

References 15 publications

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“…−1 for YFe 2 , reaches a broad maximum for intermediate concentrations, and drops sharply to zero near the critical Co concentration [11]. The pseudo-binary Laves phases Y(Fe 1−x Co x ) 2 exhibit both extraordinary magnetic properties [7,[12][13][14][15] and ability to absorb hydrogen [16][17][18][19]. Moreover, the DyFe 2 /YFe 2 magnetic thin films are reversible exchange-spring magnets [20,21] and the YCo 2 alloys with rare-earth elements R 1−x Y x Co 2 (R = Er, Gd) are considered as magnetocaloric materials for application in magnetic refrigerators [22,23].…”

Section: Introductionmentioning

confidence: 99%

Electronic specific heat coefficient and magnetic properties of Y(Fe1−xCox)2 Laves phases: A combined experimental and first

et al. 2019

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We investigated experimentally and computationally the concentration dependence of electronic specific heat coefficient γ in Y(Fe 1−x Cox) 2 pseudobinary Laves phase system. The experimentally observed maximum in γ(x) around the magnetic phase transition was interpreted within the local density approximation (LDA) combined with the virtual crystal approximation (VCA). To explain the formation of the observed maximum, we analyzed theoretically the dependence of the magnetic energy, magnetic moments, densities of states, and Fermi surfaces on the Co concentration. Furthermore, we carried out the calculations of density of states at the Fermi level as a function of fixed spin moment. The calculated Co concentration at which γ takes the maximum value (x max-LDA-VCA = 0.91) stays in good agreement with the measured value (x max-expt = 0.925). We conclude that the observed maximum in γ(x) results from the presence of the sharp DOS peak in the vicinity of the Fermi level. FIG. 1. Crystal structure of the cubic MgCu 2 -type Laves phase.

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Section: Introductionmentioning

confidence: 99%

Electronic specific heat coefficient and magnetic properties of Y(Fe1−xCox)2 Laves phases: A combined experimental and first

et al. 2019

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“…More recently, modified versions of this source design 52 have emerged which enable room temperature direct current (DC) sputtering, 53 pulsed sputtering, 54,55 pulsed gas aggregation, 56 and perhaps, most importantly, sputtering of multiple independent targets in the same region of gas aggregation. 57,58 Collectively, these different source configurations have been used to prepare a diverse range of nanomaterials on surfaces for studies in catalysis, 46,59,60 photovoltaics, 61,62 magnetism, [63][64][65] cluster-surface interactions, [66][67][68] hydrophobic coatings, 69 mass-spectrometry imaging, 70 and optical spectroscopy. 71 It should be noted, however, that all of these source designs produce a distribution of nanoparticle sizes and compositions that must be filtered in the gas-phase using mass-spectrometry techniques in order to prepare a well-defined beam of selected particles for subsequent deposition onto surfaces.…”

Section: Introductionmentioning

confidence: 99%

Soft landing of bare nanoparticles with controlled size, composition, and morphology

2015

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Physical synthesis employing magnetron sputtering and gas aggregation in a modified commercial source has been coupled with size-selection and ion soft landing to prepare bare nanoparticles on surfaces with controlled coverage, size, composition, and morphology. Employing atomic force microscopy (AFM) and scanning electron microscopy (SEM), it is demonstrated that the size and coverage of nanoparticles on flat and stepped surfaces may be controlled using a quadrupole mass filter and the length of deposition, respectively. AFM shows that nanoparticles bind randomly to flat surfaces when soft landed at relatively low coverage (4 × 10(4) ions μm(-2)). On stepped surfaces at intermediate coverage (4 × 10(5) ions μm(-2)) nanoparticles bind along step edges forming extended linear chains. At the highest coverage (2 × 10(6) ions μm(-2)) nanoparticles form a continuous film on flat surfaces. On one surface with sizable defects, the presence of localized imperfections results in agglomeration of nanoparticles onto these features and formation of neighboring zones devoid of particles. Employing high resolution scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) the customized magnetron sputtering/gas aggregation source is demonstrated to produce bare single metal particles with controlled morphology as well as bimetallic alloy nanoparticles with defined core-shell structures of that are of interest to catalysis.

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“…Haberland and co-workers first demonstrated this physical synthesis technique in 1991 to study the creation of thin films on surfaces through energetic cluster deposition. [33][34][35][36][37][38][39] Together, these different source con-figurations have been employed to prepare a wide range of nanoparticles and clusters on surfaces for studies in catalysis, 40,41 photovoltaics, 42,43 magnetism, [44][45][46] cluster-surface interactions and self-assembly, [47][48][49] as well as hydrophobic coatings. 29 Recently, modified versions of this source design have emerged which enable room temperature direct current (DC) sputtering, 30 pulsed sputtering, 31,32 and sputtering of multiple independent targets in one region of gas aggregation.…”

Section: Introductionmentioning

confidence: 99%

“…29 Recently, modified versions of this source design have emerged which enable room temperature direct current (DC) sputtering, 30 pulsed sputtering, 31,32 and sputtering of multiple independent targets in one region of gas aggregation. [33][34][35][36][37][38][39] Together, these different source con-figurations have been employed to prepare a wide range of nanoparticles and clusters on surfaces for studies in catalysis, 40,41 photovoltaics, 42,43 magnetism, [44][45][46] cluster-surface interactions and self-assembly, [47][48][49] as well as hydrophobic coatings. 50 All of these sources, however, produce a broad distribution of ionic nanoparticles that must be filtered in the gas-phase with mass-spectrometry techniques to prepare a precisely-defined (mass-selected) beam of ionic particles for controlled deposition onto surfaces.…”

Section: Introductionmentioning

confidence: 99%

Soft landing of bare PtRu nanoparticles for electrochemical reduction of oxygen

et al. 2015

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Magnetron sputtering of two independent Pt and Ru targets coupled with inert gas aggregation in a modified commercial source has been combined with soft landing of mass-selected ions to prepare bare 4.5 nm diameter PtRu nanoparticles on glassy carbon electrodes with controlled size and morphology for electrochemical reduction of oxygen in solution. Employing atomic force microscopy (AFM) it is shown that the nanoparticles bind randomly to the glassy carbon electrode at a relatively low coverage of 7 × 10(4) ions μm(-2) and that their average height is centered at 4.5 nm. Scanning transmission electron microscopy images obtained in the high-angle annular dark field mode (HAADF-STEM) further confirm that the soft-landed PtRu nanoparticles are uniform in size. Wide-area scans of the electrodes using X-ray photoelectron spectroscopy (XPS) reveal the presence of both Pt and Ru in atomic concentrations of ∼9% and ∼33%, respectively. Deconvolution of the high energy resolution XPS spectra in the Pt 4f and Ru 3d regions indicates the presence of both oxidized Pt and Ru. The substantially higher loading of Ru compared to Pt and enrichment of Pt at the surface of the nanoparticles is confirmed by wide-area analysis of the electrodes using time-of-flight medium energy ion scattering (TOF-MEIS) employing both 80 keV He(+) and O(+) ions. The activity of electrodes containing 7 × 10(4) ions μm(-2) of bare 4.5 nm PtRu nanoparticles toward the electrochemical reduction of oxygen was evaluated employing cyclic voltammetry (CV) in 0.1 M HClO4 and 0.5 M H2SO4 solutions. In both electrolytes a pronounced reduction peak was observed during O2 purging of the solution that was not evident during purging with Ar. Repeated electrochemical cycling of the electrodes revealed little evolution in the shape or position of the voltammograms indicating high stability of the nanoparticles supported on glassy carbon. The reproducibility of the nanoparticle synthesis and deposition was evaluated by employing the same experimental parameters to prepare nanoparticles on glassy carbon electrodes on three occasions separated by several days. Surfaces with almost identical electrochemical behavior were observed with CV, demonstrating the highly reproducible preparation of bare nanoparticles using physical synthesis in the gas-phase combined with soft landing of mass-selected ions.

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Magnetism of cluster-deposited Y–Co nanoparticles

Cited by 9 publications

References 15 publications

Electronic specific heat coefficient and magnetic properties of Y(Fe1−xCox)2 Laves phases: A combined experimental and first

Electronic specific heat coefficient and magnetic properties of Y(Fe1−xCox)2 Laves phases: A combined experimental and first

Soft landing of bare nanoparticles with controlled size, composition, and morphology

Soft landing of bare PtRu nanoparticles for electrochemical reduction of oxygen

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