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Full-Text Articles in Physics
First Principles Study Of Transition-Metal Substitutions In Sm–Co Permanent Magnets, Renat F. Sabirianov, Arti Kashyap, Ralph Skomski, Sitaram Jaswal, David J. Sellmyer
First Principles Study Of Transition-Metal Substitutions In Sm–Co Permanent Magnets, Renat F. Sabirianov, Arti Kashyap, Ralph Skomski, Sitaram Jaswal, David J. Sellmyer
David Sellmyer Publications
The microchemistry and magnetism of conventional and high-temperature Sm–Co permanent magnets are investigated by first-principles calculations. Particular emphasis is on the site preference for the substitution of Cu, Ti, and Zr in SmCo5 and Sm2Co17 compounds. Cu substitution is more favorable in the 1:5 phase, in agreement with experimental findings. Titanium and zirconium have positive solution energies for both the phases, with Ti(Zr) having slight preference for the 1:5 (2:17) phase. Some Zr may segregate to the phase boundaries because of its large solution energy. For Ti and Zr the dumbbell site of the 2:17 phase …
Growth And Magnetism Of Fept:C Composites In Nanoscale Channels, Yucheng Sui, J. Zhou, Xingzhong Li, Ralph Skomski, David J. Sellmyer
Growth And Magnetism Of Fept:C Composites In Nanoscale Channels, Yucheng Sui, J. Zhou, Xingzhong Li, Ralph Skomski, David J. Sellmyer
David Sellmyer Publications
Nanochannels of porous alumina films were used as nanoreactors for the reaction of hydrogen gas with a mixture of Fe nitrate and Pt chloride. This results in the formation of of FePt clusters within the nanochannels. Both the sizes of the clusters and the coercivity the cluster assembly increase with the increase of annealing temperature. In order to reduce excessive agglomeration at high temperature, carbon was introduced by chemical vapor deposition and FePt:C composites in nanoscale channels were created. When FePt clusters were synthesized with carbon and heat treated at high temperatures, cluster sizes were much smaller than those without …
Multidomain And Incoherent Effects In Magnetic Nanodots, Ralph Skomski, Arti Kashyap, Kory D. Sorge, David J. Sellmyer
Multidomain And Incoherent Effects In Magnetic Nanodots, Ralph Skomski, Arti Kashyap, Kory D. Sorge, David J. Sellmyer
David Sellmyer Publications
The magnetic ground state and the magnetization reversal of aspherical nanoparticles are investigated by model calculations and micromagnetic simulations. Essential deviations from Kittel's domain theory occur for very flat and very elongated particles, for particles whose size is comparable to the domain-wall width, and when the particle shape is strongly nonellipsoidal. For example, the single-domain state of square rod is much less stable than that of comparable elongated ellipsoids, because most of the surface charge of long ellipsoids is located on the sides. Another specific feature of flat particles is suppression of the curling mode.
Magnetic Nanotubes Produced By Hydrogen Reduction, Yucheng Sui, Ralph Skomski, Kory D. Sorge, David J. Sellmyer
Magnetic Nanotubes Produced By Hydrogen Reduction, Yucheng Sui, Ralph Skomski, Kory D. Sorge, David J. Sellmyer
David Sellmyer Publications
FePt and Fe3O4 nanotubes are produced by hydrogen reduction in nanochannels of porous alumina templates and investigated by electron microscopy, x-ray diffraction, and superconducting quantum interference device magnetometry. Loading the templates with an Fe chloride and Pt chloride mixture, followed by hydrogen reduction at 560 °C, leads to the formation of ferromagnetic FePt nanotubes in the alumina pores. An Fe nitrate solution, thermally decomposed at 250 °C and reduced in hydrogen for 2.5 h at the same temperature, yields Fe3O4 tubes. The versatility of the method indicates that materials with a wide range of …
Magnetism Of L10 Compounds With The Composition Mt (M = Rh, Pd, Pt, Ir And T = Mn, Fe, Co, Ni), Arti Kashyap, Ralph Skomski, Ashok K. Solanki, Yinfan Xu, David J. Sellmyer
Magnetism Of L10 Compounds With The Composition Mt (M = Rh, Pd, Pt, Ir And T = Mn, Fe, Co, Ni), Arti Kashyap, Ralph Skomski, Ashok K. Solanki, Yinfan Xu, David J. Sellmyer
David Sellmyer Publications
The electronic band structure of ordered equiatomic compounds of 3d transition elements (Mn, Fe, Co, Ni) with nonmagnetic 4d and 5d elements (Rh, Pd, Pt, Ir) are investigated by linear muffin-tin orbital calculations. The systematic study considers 3d and 4d/5d spin moments and interatomic exchange interactions, with emphasis on the comparison between ferromagnetic and antiferromagnetic order. Total and site-resolved exchange interactions are calculated from first principles, and the obtained exchange constants are used to estimate ordering temperatures on a mean-field level.