129 research outputs found
Non-reciprocal light scattering by lattice of magnetic vortices
We report on experimental study of optical properties of two-dimensional
square lattice of triangle Co and CoFe nanoparticles with a vortex
magnetization distribution. We demonstrate that intensity of light scattered in
diffraction maxima depends on the vorticity of the particles magnetization and
it can be manipulated by applying an external magnetic field. The experimental
results can be understood in terms of phenomenological theory.Comment: 10 pages, 4 figure
Electron-ion-plasma modification of the structure and properties of commercial steels
The work is devoted to the structural-phase analysis of steels of the austenitic and martensitic grade, irradiated with a high-intensity pulsed electron beam of the submillisecond duration of exposure in the mode of the surface layer melting. A thermodynamic analysis of phase transformations occurring during heat treatment in alloys of the composition Fe-Cr-C and Fe-Cr-Ni-C, which are the basis of steels 20X13 and 12X18H10T, is carried out. It is shown that formation of solid solutions on the basis of [alpha]-iron (BCC crystalline lattice) and [gamma]- iron (FCC crystalline lattice) as well as the entire range of carbide phases of a complex elemental composition (M[23]C[6], M[7]C[3] и M[3]C, where symbol M refers to atoms of metallic elements Fe, Cr, and Ni) is possible in equilibrium conditions in given materials. The irradiation of steels 12X18H10T and 20X13 with a high-intensity pulsed electron beam of the submillisecond duration of exposure is carried out. It is shown that the electron-beam processing of steel in the melting mode and the subsequent rapid crystallization is accompanied by a significant transformation of the surface layer structure, consisting in complete dissolution of original carbide phase particles; in formation of dendritic crystallization cells of submicron sizes; in occurrence of martensitic [gamma]->[alpha] and [gamma]->[epsilon] transformation; in re-allocation of nanosized particles of carbide and intermetallic phases
Considerable enhancement of the critical current in a superconducting film by magnetized magnetic strip
We show that a magnetic strip on top of a superconducting strip magnetized in
a specified direction may considerably enhance the critical current in the
sample. At fixed magnetization of the magnet we observed diode effect - the
value of the critical current depends on the direction of the transport
current. We explain these effects by a influence of the nonuniform magnetic
field induced by the magnet on the current distribution in the superconducting
strip. The experiment on a hybrid Nb/Co structure confirmed the predicted
variation of the critical current with a changing value of magnetization and
direction of the transport current.Comment: 6 pages, 7 figure
Anti-vortex state in cross-like nanomagnets
We report on results of computer micromodelling of anti-vortex states in
asymmetrical cross-like ferromagnetic nanostructures and their practical
realization. The arrays of cobalt crosses with 1 mkm branches, 100 nm widths of
the branches and 40 nm thicknesses were fabricated using e-beam lithography and
ion etching. Each branch of the cross was tapered at one end and bulbous at the
other. The stable formation of anti-vortex magnetic states in these
nanostructures during magnetization reversal was demonstrated experimentally
using magnetic force microscopy.Comment: 19 pages, 9 figure
Magnetic force microscope tip-induced remagnetization of CoPt nanodisks with perpendicular anisotropy
We report on the results of a magnetic force microscopy investigation of remagnetization processes in arrays of CoPt nanodisks with diameters of 35 and 200 nm and a thickness of 9.8 nm fabricated by e-beam lithography and ion etching. The controllable magnetization reversal of individual CoPt nanodisks by the magnetic force microscope (MFM) tip-induced magnetic field was demonstrated. We observed experimentally two essentially different processes of tip-induced remagnetization. Magnetization reversal of 200 nm disks was observed when the probe moved across the particle while in case of 35 nm nanodisks one-touch remagnetization was realized. Micromagnetic modeling based on the Landau-Lifshitz-Gilbert (LLG) equation demonstrated that the tip-induced magnetization reversal occurs through the essentially inhomogeneous states. Computer simulations confirmed that in case of 200 nm disks the mechanism of embryo nucleation with reversed magnetization and further dynamic propagation following the probe moving across the particle was realized. On the other hand one-touch remagnetization of 35 nm disks occurs through the inhomogeneous vortexlike state. Micromagnetic LLG simulations showed that magnetization reversal in an inhomogeneous MFM probe field has a lower energy barrier in comparison with the mechanism of coherent rotation, which takes place in a homogeneous external magnetic field
Monte Carlo Simulations of Powerful Neutron Interaction with Matter for the Goals of Disclosure of Hidden Explosives and Fissile Materials and for Treatment of Cancer Diseases versus their Experimental Verifications
Neutral and Cationic Rare Earth Metal Alkyl and Benzyl Compounds with the 1,4,6-Trimethyl-6-pyrrolidin-1-yl-1,4-diazepane Ligand and Their Performance in the Catalytic Hydroamination/Cyclization of Aminoalkenes
A new neutral tridentate 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-diazepane (L) was prepared. Reacting L with trialkyls M(CH2SiMe3)3(THF)2 (M = Sc, Y) and tribenzyls M(CH2Ph)3(THF)3 (M = Sc, La) yielded trialkyl complexes (L)M(CH2SiMe3)3 (M = Sc, 1; M = Y, 2) and tribenzyl complexes (L)M(CH2Ph)3 (M = Sc, 3; M = La, 4). Complexes 1 and 2 can be converted to their corresponding ionic compounds [(L)M(CH2SiMe3)2(THF)][B(C6H5)4] (M = Sc, Y) by reaction with [PhNMe2H][B(C6H5)4] in THF. Complexes 3 and 4 can be converted to cationic species [(L)M(CH2Ph)2]+ by reaction with [PhNMe2H][B(C6F5)4] in C6D5Br in the absence of THF. The neutral complexes 1-4 and their cationic derivatives were studied as catalysts for the hydroamination/cyclization of 2,2-diphenylpent-4-en-1-amine and N-methylpent-4-en-1-amine reference substrates and compared with ligand-free Sc, Y, and La neutral and cationic catalysts. The most effective catalysts in the series were the cationic L-yttrium catalyst (for 2,2-diphenylpent-4-en-1-amine) and the cationic lanthanum systems (for N-methylpent-4-en-1-amine). For the La catalysts, evidence was obtained for release of L from the metal during catalysis.
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