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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Soliton motion induced along ferromagnetic skyrmion chains in chiral thin nanotracks

Using atomistic magnetic simulations we investigate the soliton motion along a pinned skyrmion chain containing an interstitial skyrmion. We find that the soliton can exhibit stable motion along the chain without a skyrmion Hall effect for an extended range of drives. Under a constant drive the solitons have a constant velocity. We also measure the skyrmion velocity–current curves and identify the signatures of different phases including a pinned phase, stable soliton motion, and quasi-free motion at higher drives where all of the skyrmions depin from the pinning centers and move along the rigid wall. In the quasi-free motion regime, the velocity is oscillatory due to the motion of the skyrmions over the pinning sites. For increasing pinning strength, the onset of soliton motion shifts to higher values of current density. We also find that for stronger pinning, the characteristic velocity–current shape is affected by the annihilation of single or multiple skyrmions in the drive interval over which the soliton motion occurs. Our results indicate that stable skyrmion soliton motion is possible and that the solitons could be used as information carriers instead of the skyrmions themselves for technological applications.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Intrinsic magnetic, structural and resistivity properties of ferromagnetic Mn{sub 0.5}Zn{sub 0.5}Al{sub x}Fe{sub 2−x}O{sub 4} nanoparticles

Highlights: ► Al{sup 3+} ion substituted Mn–Zn ferrite nanoparticles. ► Single phase cubic spinel structure changes with Al{sup 3+} substitution. ► Magnetization and coercivity decreased with increasing Al{sup 3+}. ► Resistivity increased with Al{sup 3+} substitution. - Abstract: In this work the nano-structural, magnetic and resistivity properties of Al{sup 3+} substituted Mn–Zn ferrites powders were investigated. Mn{sub 0.5}Zn{sub 0.5}Al{sub x}Fe{sub 2−x}O{sub 4} powders, where x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 were obtained by the sol–gel auto-combustion method. X-ray diffraction data indicate that, after substitution, all the samples consisted of the main spinel phase in combination with a small amount of a foreign Al{sub 2}O{sub 3} phase. The addition of Al{sup 3+} resulted in a reduction of particle size and density of the prepared samples. Cation distribution in the present study was estimated by using X-ray diffraction data. The tetrahedral site radii initially increased with Al{sup 3+} content while the octahedral site radii decreased with the Al{sup 3+} substitution. FTIR spectra show two strong absorption bands at 529–548 cm{sup −1} and 445–452 cm{sup −1} which are the typical bands for the cubic spinel crystal structure. The magnetic properties were measured by employing a vibrating sample magnetometer. It was observed that the saturation magnetization, coercivity and anisotropy field decreased with the increase of Al{sup 3+} substitution. Introduction of Al{sup 3+} ions into the Mn–Zn ferrite increased the values of the resistivity, especially in the lower temperature range.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Unoccupied electronic structure of Ni 2 MnGa ferromagnetic shape memory alloy

Momentum resolved inverse photoemission spectroscopy measurements show that the dispersion of the unoccupied bands of Ni 2 MnGa is significant in the austenite phase. Furthermore, in the martensite phase, it is markedly reduced, which is possibly related to the structural transition to an incommensurate modulated state in the martensite phase. Finally, based on the first principle calculations of the electronic structure of Ni–Mn–Ga, we show that the modification of the spectral shape with surface composition is related to change in the hybridization between the Mn 3d and Ni 3d-like states that dominate the unoccupied conduction band.

36 MATERIALS SCIENCE↗