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RISS 인기검색어
- 검색키워드
- 저자 : Lomakin, V. (검색결과 3 건)
- 무료
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Fast Optimal Design of Micromagnetic Devices Using FastMag and Distributed Evolutionary Algorithm
Jin-Kyu Byun,Volvach, Iana,Lomakin, Vitaliy IEEE 2016 IEEE transactions on magnetics Vol.52 No.9
<P>A new software framework is presented for fast optimal designs of micromagnetic devices. The developed framework adopts a fast micromagnetic (FastMag) simulator as a micromagnetic solver, and utilizes distributed evolutionary algorithm in Python (DEAP). The framework makes use of a simple Linux utility for resource management (SLURM) in order to run and manage multiple micromagnetic simulations concurrently on a Linux cluster. Various design variables can be designated including material and geometry parameters. The whole design cycle is automated including the mesh generation, and the status of the evolution and multiple simulations can be monitored and managed easily. By combining high computing speed of FastMag and distributed optimization capability of DEAP and SLURM, the optimal designs of micromagnetic devices can be performed rapidly and efficiently. As numerical examples, the optimal designs of a spin-torque oscillator and a magnetic random access memory device are performed.</P>
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Tailoring magnetic energies to form dipole skyrmions and skyrmion lattices
Montoya, S. A.,Couture, S.,Chess, J. J.,Lee, J. C. T.,Kent, N.,Henze, D.,Sinha, S. K.,Im, M.-Y.,Kevan, S. D.,Fischer, P.,McMorran, B. J.,Lomakin, V.,Roy, S.,Fullerton, E. E. American Physical Society 2017 Physical Review B Vol.95 No.2
<P>The interesting physics and potential memory technologies resulting from topologically protected spin textures such as skyrmions have prompted efforts to discover new material systems that can host these kinds of magnetic structures. Here, we use the highly tunable magnetic properties of amorphous Fe/Gd multilayer films to explore the magnetic properties that lead to dipole-stabilized skyrmions and skyrmion lattices that form from the competition of dipolar field and exchange energy. Using both real space imaging and reciprocal space scattering techniques, we determined the range of material properties and magnetic fields where skyrmions form. Micromagnetic modeling closely matches our observation of small skyrmion features (similar to 50 to 70 nm) and suggests that these classes of skyrmions have a rich domain structure that is Bloch-like in the center of the film and more Neel-like towards each surface. Our results provide a pathway to engineer the formation and controllability of dipole skyrmion phases in a thin film geometry at different temperatures and magnetic fields.</P>
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Resonant properties of dipole skyrmions in amorphous Fe/Gd multilayers
Montoya, S. A.,Couture, S.,Chess, J. J.,Lee, J. C. T.,Kent, N.,Im, M.-Y.,Kevan, S. D.,Fischer, P.,McMorran, B. J.,Roy, S.,Lomakin, V.,Fullerton, E. E. American Physical Society 2017 Physical Review B Vol.95 No.22
<P>The dynamic response of dipole skyrmions in Fe/Gd multilayer films is investigated by ferromagnetic resonance measurements and compared to micromagnetic simulations. We detail thickness-and temperature-dependent studies of the observed modes as well as the effects of magnetic field history on the resonant spectra. Correlation between the modes and the magnetic phase maps constructed from real-space imaging and scattering patterns allows us to conclude that the resonant modes arise from local topological features such as dipole skyrmions but do not depend on the collective response of a close-packed lattice of these chiral textures. Using micromagnetic modeling, we are able to quantitatively reproduce our experimental observations which suggests the existence of localized spin-wave modes that are dependent on the helicity of the dipole skyrmion. We identify four localized spin-wave excitations for the skyrmions that are excited under either in-plane or out-of-plane rf fields. Lastly we show that dipole skyrmions and nonchiral bubble domains exhibit qualitatively different localized spin-wave modes.</P>
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