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Full-Text Articles in Physics
Fabrication Of Chromium Oxide Nanoparticles By Laser-Induced Deposition From Solution, Z.C. Zhong, R.H. Cheng, Jocelyn Bosley, Peter A. Dowben, David J. Sellmyer
Fabrication Of Chromium Oxide Nanoparticles By Laser-Induced Deposition From Solution, Z.C. Zhong, R.H. Cheng, Jocelyn Bosley, Peter A. Dowben, David J. Sellmyer
David Sellmyer Publications
We have successfully deposited well-dispersed nanoscale chromium oxide particles by laser-induced solution deposition (LISD) from solution with CrCl2 and organic solvents. The particles have narrow distributions about three sizes: 230, 350 and 400 nm and are uniform in composition and contain little contamination. We show that LISD is a new technique for producing nanoparticle chromium oxides with uniform composition, controllable size and high yield.
High-Temperature Magnetic Properties Of Mechanically Alloyed Smco 5 And Yco5 Magnets, I.A. Al-Omari, Ralph Skomski, R.A. Thomas, D. Leslie-Pelecky, David J. Sellmyer
High-Temperature Magnetic Properties Of Mechanically Alloyed Smco 5 And Yco5 Magnets, I.A. Al-Omari, Ralph Skomski, R.A. Thomas, D. Leslie-Pelecky, David J. Sellmyer
David Sellmyer Publications
The high-temperature coercivity of mechanically alloyed and subsequently annealed RCo5 (R=Sm and Y) is studied. The annealed materials have the hexagonal CaCu5 structure with 2 : 17 (or 1 : 7) regions as a minor phase. High-temperature magnetic measurements showthat the coercivities of materials decrease with increasing temperature fromroom-temperature to 873 K, but that the temperature coefficient of the coercivity of YCo5 is much smaller than that of SmCo5. This behavior is explained in terms of the intrinsic temperature variation of the magnetocrystalline anisotropy.
Coercivity Of Titanium-Substituted High-Temperature Permanent Magnets, Jian Zhou, Ralph Skomski, David J. Sellmyer
Coercivity Of Titanium-Substituted High-Temperature Permanent Magnets, Jian Zhou, Ralph Skomski, David J. Sellmyer
David Sellmyer Publications
The temperature dependence of the coercivity of Sm–Co based magnets is investigated by magnetization measurements and model calculations. The Zr-free titanium-substituted Sm–Co material exhibits a positive temperature coefficient dHc/dT of the coercivity (TCC) above room temperature, a reasonable hysteresis-loop shape, and an appreciable coercivity of 12.3 kOe at 500 C for the nominal composition Sm(Co6.2Cu0.8Ti0.3). The samples were produced by heat-treating the disordered 1 : 5 alloy commonly referred to as the TbCu7 (or 1 : 7) phase. X-ray diffraction analysis shows that, upon annealing at 1165 C, …
Grain-Boundary Micromagnetism, Ralph Skomski, H. Zeng, David J. Sellmyer
Grain-Boundary Micromagnetism, Ralph Skomski, H. Zeng, David J. Sellmyer
David Sellmyer Publications
Continuum and layer-resolved calculations are used to investigate the spin structure in the vicinity of grain boundaries. Reduced exchange in the grain-boundary region gives rise to a quasidiscontinuity of the magnetization and yields a perturbation which decays exponentially inside the grains. An effective intergranular exchange is obtained as a micromagnetically well-defined function of the grain-boundary exchange, and it is discussed how grain boundaries affect the hysteresis loops of nanostructures.
Cooperative Magnetism And The Preisach Model, Ralph Skomski, David J. Sellmyer
Cooperative Magnetism And The Preisach Model, Ralph Skomski, David J. Sellmyer
David Sellmyer Publications
Cooperative and noncooperative magnetization processes in magnetic nanostructures are investigated. Using model calculations it is shown that the Preisach model and related approaches, such as Henkel, ΔM, and ΔH plots, describe magnetism on a mean-field level and cannot account for intra- and inter-granular cooperative effects. For example, the ΔM plot of a nucleation-controlled two-domain particle gives the false impression of a positive intergranular interaction. A simple but nontrivial cooperative model, consisting of two interacting but nonequivalent particles, is used to show that cooperative effects are most pronounced for narrow switching-field distributions, i.e., for nearly rectangular loops. …
Coptcr:C Nanocomposite Films For High Density Recording, H. Zeng, M.L. Yan, Yi Liu, David J. Sellmyer
Coptcr:C Nanocomposite Films For High Density Recording, H. Zeng, M.L. Yan, Yi Liu, David J. Sellmyer
David Sellmyer Publications
We report results on the magnetic properties of nanocomposite films of the form (Co86Cr14)xPt1-x:C, which were prepared by magnetron sputtering and subsequent annealing. X-ray diffraction shows that these films consist of CoPtCr grains with the face-centered-tetragonal structure embedded in an amorphous C matrix. Magnetic properties such as coercivity (Hc), remanence ratio (S), and coercive squareness (S*) are strongly dependent on the Pt and C composition and annealing temperatures. Compared with previously reported CoPt:C films with a equiatomic Co and Pt ratio, lower exchange coupling and …