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Articles 1 - 8 of 8
Full-Text Articles in Physics
Magnetism Of Films, Yi Liu, David J. Sellmyer
Magnetism Of Films, Yi Liu, David J. Sellmyer
David Sellmyer Publications
Films of L10-structure Fe50–xCoxPt50 films are synthesized by co-sputtering Fe, Co, and Pt on (001) MgO substrates and Si substrates with in-situ heating at 830°C. The nanostructures and magnetic properties of the films are characterized by X-ray diffraction, transmission electron microscopy, and SQUID. The compositions of the samples Fe50–xCoxPt50 are designed to maintain an atomic (Fe+Co):Pt ratio of 50:50 while increasing the Co content in each successive sample. In all samples, the X-ray diffraction patterns from samples on MgO substrate exhibit three strong peaks, namely L10Fe50–xCoxPt50 (001), (002), and MgO (002). The X-ray and electron diffraction patterns from …
Structural And Magnetic Properties Of Pr-Alloyed Mnbi Nanostructures, Parashu Kharel, Shah R. Valloppilly, Xingzhong Li, Wenyong Zhang, Ralph Skomski, Jeffrey E. Shield, David J. Sellmyer
Structural And Magnetic Properties Of Pr-Alloyed Mnbi Nanostructures, Parashu Kharel, Shah R. Valloppilly, Xingzhong Li, Wenyong Zhang, Ralph Skomski, Jeffrey E. Shield, David J. Sellmyer
David Sellmyer Publications
The structural and magnetic properties of Pr-alloyed MnBi (short MnBi-Pr) nanostructures with a range of Pr concentrations are investigated. The nanostructures include thin films having Pr concen-trations 0, 2, 3, 5, and 9 at.% and melt-spun ribbons having Pr concentrations 0%, 2%, 4%, and 6%, respectively. Addition of Pr into the MnBi lattice has produced a significant change in the magnetic properties of these nanostructures, including an increase in coercivity and structural phase transition temperature, and a decrease in saturation magnetization and anisotropy energy. The highest value of coercivity measured in the films is 23 kOe and in the ribbons …
Low Temperature Ordering And High (001) Orientation Of [Fe/Pt/Cu]18 Multilayer Films, Yongsheng Yu, Xingzhong Li, T A. George, W D. Fei, Haibo Li, David J. Sellmyer
Low Temperature Ordering And High (001) Orientation Of [Fe/Pt/Cu]18 Multilayer Films, Yongsheng Yu, Xingzhong Li, T A. George, W D. Fei, Haibo Li, David J. Sellmyer
David Sellmyer Publications
[Fe/Pt/Cu]18 multilayer films with different Cu thicknesses were prepared on thermally oxidized Si (111) substrates at room temperature using dc- and rf-magnetron sputtering. The magnetic proper-ties and microstructure of [Fe/Pt/Cu]18 multilayer films annealed at various temperatures have been investigated. Compared with pure [Fe/Pt]18 multilayer films low-temperature ordering and (001) ori-entation in the annealed films with Cu volume concentration below 20% can be obtained. During annealing process Cu atoms diffused into FePt lattice which enhanced the diffusion of Fe and Pt atoms and the grain growth of the films. The perpendicular anisotropy and hard magnetic properties of the …
One-Pot Synthesis Of Urchin-Like Fepd−Fe3O4 And Their Conversion Into Exchange-Coupled L10−Fepd−Fe Nanocomposite Magnets, Yongsheng Yu, Kewei Sun, Yuan Tian, Xingzhong Li, Matthew J. Kramer, David J. Sellmyer, Jeffrey E. Shield, Shouheng Sun
One-Pot Synthesis Of Urchin-Like Fepd−Fe3O4 And Their Conversion Into Exchange-Coupled L10−Fepd−Fe Nanocomposite Magnets, Yongsheng Yu, Kewei Sun, Yuan Tian, Xingzhong Li, Matthew J. Kramer, David J. Sellmyer, Jeffrey E. Shield, Shouheng Sun
David Sellmyer Publications
We report a one-pot synthesis of urchin-like FePd−Fe3O4 nanocomposites, spherical clusters of FePd nanoparticles (NPs) with spikes of Fe3O4 nanorods (NRs), via controlled thermal decomposition of Fe(CO)5 and reduction of Pd(acac)2. The FePd NPs with sizes between 6 and 9 nm self-aggregate into 60 nm superparticles (SPs), and Fe3O4 NRs grow on the surface of these SPs. Reductive annealing at 500°C converts the FePd−Fe3O4 into exchange-coupled nanocomposites L10−FePd−Fe with their Hc tunable from 0.8 to 2.6 kOe and Ms controlled from 90 to …
Effect Of Exchange Interactions On The Coercivity Of Smco5 Nanoparticles Made By Cluster Beam Deposition, O Akdogan, W Li, B Balasubrmanian, David J. Sellmyer, George C. Hadjipanayis
Effect Of Exchange Interactions On The Coercivity Of Smco5 Nanoparticles Made By Cluster Beam Deposition, O Akdogan, W Li, B Balasubrmanian, David J. Sellmyer, George C. Hadjipanayis
David Sellmyer Publications
Single crystal SmCo5 nanoparticles with an average size of 3.5 nm are produced by cluster-beam deposition. When deposited without matrix, the nanoparticles showed a super-paramagnetic be-havior with a blocking temperature of 145 K. Dispersion of the SmCo5 nanoparticles in a carbon matrix results in an increase in both the coercivity and the blocking temperature. Room temperature coercivities as high as 12 kOe are obtained for the first time in mono-layers of SmCo5 nanoparticles dispersed in C matrix. δM plots show that the interactions in the samples are of exchange type, which can decrease the overall effective …
Novel Nanostructured Rare-Earth-Free Magnetic Materials With High Energy Products, Balamurugan Balasubramanian, Bhaskar Das, Ralph Skomski, Wenyong Zhang, David J. Sellmyer
Novel Nanostructured Rare-Earth-Free Magnetic Materials With High Energy Products, Balamurugan Balasubramanian, Bhaskar Das, Ralph Skomski, Wenyong Zhang, David J. Sellmyer
David Sellmyer Publications
The development of new iron- or cobalt-rich permanent-magnet materials is of paramount importance in materials science and technology since high-performance materials based on Nd2Fe14B or FePt are extremely expensive or subject to limited rare-earth supplies.[1–4] Aside from phase-diagram considerations, this requires alloys with high magnetocrystal-line anisotropy K1 and Curie temperature Tc. However, the range of alternative compounds with appreciable K1 and high Tc is limited, and the situation is often aggravated by their metastable nature and by the requirement of high-formation temperatures.[5–12] For exam-ple, two suitable candidates are Zr2Co11 and HfCo …
Solubility Extension And Phase Formation In Gas-Condensed Co–W Nanoclusters, Farhad Golkar, Matthew J. Kramer, Ames Laboratory, Ralph A. Skomski, David J. Sellmyer, Jeffrey E. Shield
Solubility Extension And Phase Formation In Gas-Condensed Co–W Nanoclusters, Farhad Golkar, Matthew J. Kramer, Ames Laboratory, Ralph A. Skomski, David J. Sellmyer, Jeffrey E. Shield
David Sellmyer Publications
Co–W alloy clusters with extended solubility of W in hcp Co were produced by inert-gas condensa-tion. 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 clus-ters, 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 …
Magnetism Of Rapidly Quenched Rhombohedral Zr2Co11-Based Nanocomposites, Wenyong Zhang, Xingzhong Li, Shah R. Valloppilly, Ralph A. Skomski, Jeffrey E. Shield, David J. Sellmyer
Magnetism Of Rapidly Quenched Rhombohedral Zr2Co11-Based Nanocomposites, Wenyong Zhang, Xingzhong Li, Shah R. Valloppilly, Ralph A. Skomski, Jeffrey E. Shield, David J. Sellmyer
David Sellmyer Publications
The effect of quench rate and Zr content on nanostructure and magnetic properties of melt-spun ZrxCo100−x (x = 16–21) is investigated. High quench rate favors the formation of rhombohedral Zr2Co11, which is the hard phase. The coercivity increases with an increase in quench rate. Zr addition in limited amounts decreases the grain size of magnetic phases, which may promote the effective ex-change coupling of soft magnetic phases. Therefore, coercivity and maximum energy product of Zr2Co11-based materials are significantly enhanced. The best magnetic properties, iHc = 3.0 kOe and (BH) …