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

TitleSolubility extension and phase formation in gas-condensed Co-W nanoclusters
Publication TypeJournal Article
Year of Publication2013
AuthorsGolkar F, Kramer MJ, Zhang Y, Skomski R, Sellmyer DJ, Shield JE
Journal TitleJournal of Nanoparticle Research
Volume15
Pages1638
Date Published05
Type of ArticleArticle
ISBN Number1388-0764
Accession NumberWOS:000318555400043
Keywordscobalt alloys, Coercive, DIAGRAMS, FORCE, metal clusters, nanoalloys, nanofabrication, nanomagnetics, nanoparticles, nanostructured materials, Sputter deposition, transmission electron microscopy, Tungsten alloys, x-ray diffraction
Abstract

Co-W alloy clusters with extended solubility of W in hcp Co were produced by inert-gas condensation. The structural state of the as-deposited Co-W 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 x 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.

URL<Go to ISI>://WOS:000318555400043
DOI10.1007/s11051-013-1638-x