Structure and magnetic properties of Co-W clusters produced by inert gas condensation

Golkar, Farhad; Kramer, M. J.; Zhang, Y.; McCallum, R. W.; Skomski, Ralph; Sellmyer, David J.; Shield, Jeffrey E.

doi:10.1063/1.3676425

Cited by 12 publications

(6 citation statements)

References 7 publications

(9 reference statements)

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“…Inert-gas condensation (IGC) is a non-equilibrium processing route to produce nanoparticles, making it an ideal technique to explore new materials and structures (Koshkin and Slezov 2004;Mukherjee et al 2012). In IGC, the cluster structure depends on processing conditions, notably the sputtering power when dc magnetron sputtering is used to create the gas phase (Balasubramanian et al 2011;Patterson et al 2010;Qiu and Wang 2006), and the temperature inside the cluster-forming chamber (Golkar et al 2012). Further, the structural state in clusters is size-dependent, especially in Co nanoclusters, where the fcc structure was predominant in sub-6 nm clusters, with the volume fraction of the hcp structure increasing with increasing cluster size (Yamamuro et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Solubility extension and phase formation in gas-condensed Co–W nanoclusters

et al. 2013

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CoW alloy clusters with extended solubility of W in hcp Co were produced by inert-gas condensation. The structural state of the as-deposited CoW clusters was found to be critically dependent on processing parameters such as the cooling scheme and sputtering power. For the water-cooled clusters, the mean size and percent crystalline were strongly dependent on sputtering power, while the percent crystalline of the liquid nitrogen-cooled clusters was not as affected by the sputtering power. At low sputtering powers, the water-cooled clusters were predominantly amorphous, but became increasingly more crystalline as the sputtering power increased. The predominant crystalline phase was hcp Co(W), but high-resolution transmission electron microscopy revealed that very small and very large clusters contained fcc and Co3W structures, respectively. For liquid nitrogen cooling the clusters were predominantly amorphous regardless of sputtering power, although at the highest sputtering power a small percentage of the clusters were crystalline. The magnetic properties were dependent on cooling schemes, sputtering power, and temperature, with the highest coercivity of 893 Oe obtained at 10 K for water-cooled clusters sputtered at 150 W. The magnetocrystalline anisotropy of the water-cooled sample increased with increasing sputtering power, with the highest anisotropy of 3.9 × 10 6 ergs/cm 3 recorded for clusters sputtered at 150 W. For liquid nitrogen-cooled samples, the anisotropy was approximately constant for all sputtering powers.

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Section: Introductionmentioning

confidence: 99%

Solubility extension and phase formation in gas-condensed Co–W nanoclusters

et al. 2013

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“…Other candidates for nonrare-earth permanent magnets are Zr Co [46] and orthorhombic HfCo [47], which have magnetzations comparable to Sm-Co, for example 1.09 T for HfCo . A problem is that the addition of and atoms, such as W, often deteriorates the magnetization [48].…”

Section: A Iron-and Cobalt-base Magnetsmentioning

confidence: 99%

Predicting the Future of Permanent-Magnet Materials

et al. 2013

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There are two main thrusts towards new permanent-magnet materials: improving extrinsic properties by nanostructuring and intrinsic properties by atomic structuring. Theory-both numerical and analytical-plays an important role in this ambitious research. Our analysis of aligned hard-soft nanostructures shows that soft-in-hard geometries are better than hard-in-soft geometries and that embedded soft spheres are better than sandwiched soft layers. Concerning the choice of the hard phase, both a high magnetization and a high anisotropy are necessary. As an example of first-principle research, we consider interatomic Mn exchange in MnAl and find strongly ferromagnetic intralayer exchange, in spite of the small Mn-Mn distances.

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“…% Cr, but unexpectedly, the presence of residual Cr inside the Ni-rich cores for higher concentrations. Golkar et al synthesized sub-10-nm Co-W clusters using inert gas condensation and studied the effects of sputtering power and temperature on the average sizes and structure of the clusters as well as their corresponding magnetic properties [24]. Furthermore, the thermodynamics and mechanisms of metallic nanoparticle preparation using inert gas condensation have been investigated using computational techniques.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics investigation of structure evolution and thermodynamics of Ni–Fe nanoparticles during inert gas condensation

Pan

Liu

et al. 2021

J Mol Model

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Synthesis of magnetic nanoparticles is relevant to many applications in the elds of catalysis, energy storage and biomedicine, etc. Understanding the growth mechanisms and morphology of nanoparticles during inert gas condensation is crucial to rationally improve the performance of the nal nanoparticles.In this work, molecular dynamics simulations are carried out to study the structural and thermodynamic behavior of Ni-Fe nanoparticles from homogenous vapor phase in Ar atmosphere. It is revealed that the nal morphology of the resulting nanoparticles presents a spherical shape by cluster coalescence at high temperatures where the small clusters are liquid droplets prior to their collisions. However, probabilistic nucleation and cluster growth indicate that the occurrence of spherical shape is more controlled by the probability limits for different Fe concentrations. Meanwhile, a larger inert gas density induces a more e cient cooling effect leading to a larger probability control of the cluster formation with non-spherical shape by agglomeration. Furthermore, the solidi cation of the as-formed Ni-Fe clusters is examined by evaluating the evolution of crystalline and amorphous structure. The linear scaling-down dependence of the solidi cation temperature on the reciprocal of the nanoparticle size clearly signi es a linear sizedepression effect for the liquid-to-solid phase change of Ni-Fe nanoparticles. Our ndings thus extend the current understanding of inert gas condensation behavior and mechanisms of Ni-Fe nanoparticles from an atomic/molecular perspective.

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Structure and magnetic properties of Co-W clusters produced by inert gas condensation

Cited by 12 publications

References 7 publications

Solubility extension and phase formation in gas-condensed Co–W nanoclusters

Solubility extension and phase formation in gas-condensed Co–W nanoclusters

Predicting the Future of Permanent-Magnet Materials

Molecular dynamics investigation of structure evolution and thermodynamics of Ni–Fe nanoparticles during inert gas condensation

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