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Norbert J Mauser - One of the best experts on this subject based on the ideXlab platform.
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computational Micromagnetics with commics
Computer Physics Communications, 2020Co-Authors: Carlmartin Pfeiler, Lukas Exl, Norbert J Mauser, G Hrkac, Michele Ruggeri, Bernhard Stiftner, Matthias Hochsteger, Joachim Schoberl, Dirk PraetoriusAbstract:Abstract We present our open-source Python module Commics for the study of the magnetization dynamics in ferromagnetic materials via micromagnetic simulations. It implements state-of-the-art unconditionally convergent finite element methods for the numerical integration of the Landau–Lifshitz–Gilbert equation. The implementation is based on the multiphysics finite element software Netgen/NGSolve. The simulation scripts are written in Python, which leads to very readable code and direct access to extensive post-processing. Together with documentation and example scripts, the code is freely available on GitLab. Program summary Program title: Commics Program Files doi: http://dx.doi.org/10.17632/29wv9h78h7.1 Licensing provisions: GPLv3 Programming language: Python3 Nature of problem: Numerical integration of the Landau–Lifshitz–Gilbert equation in three space dimensions Solution method: Tangent plane scheme [1]: original first-order version, projection-free version, second-order version, efficient second-order IMEX version; Midpoint scheme [2]: original version, IMEX version; Magnetostatic Maxwell equations are treated by the hybrid FEM–BEM method [3] Additional comments including restrictions and unusual features: An installation of the finite element software Netgen/NGSolve and an installation of the boundary element library BEM++ are required. References [1] F. Alouges. A new finite element scheme for Landau–Lifchitz equations. Discrete Contin. Dyn. Syst. Ser. S, 1(2):187–196, 2008. [2] S. Bartels and A. Prohl. Convergence of an implicit finite element method for the Landau–Lifshitz–Gilbert equation. SIAM J. Numer. Anal., 44(4):1405–1419, 2006. [3] D. R. Fredkin and T. R. Koehler. Hybrid method for computing demagnetization fields. IEEE Trans. Magn., 26(2):415–417, 1990.
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labonte s method revisited an effective steepest descent method for micromagnetic energy minimization
Journal of Applied Physics, 2014Co-Authors: Lukas Exl, Simon Bance, Franz Reichel, T Schrefl, Hans Peter Stimming, Norbert J MauserAbstract:We present a steepest descent energy minimization scheme for Micromagnetics. The method searches on a curve that lies on the sphere which keeps the magnitude of the magnetization vector constant. The step size is selected according to a modified Barzilai-Borwein method. Standard linear tetrahedral finite elements are used for space discretization. For the computation of quasistatic hysteresis loops, the steepest descent minimizer is faster than a Landau-Lifshitz micromagnetic solver by more than a factor of two. The speed up on a graphic processor is 4.8 as compared to the fastest single-core central processing unit (CPU) implementation.
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labonte s method revisited an effective steepest descent method for micromagnetic energy minimization
arXiv: Computational Physics, 2013Co-Authors: Lukas Exl, Simon Bance, Franz Reichel, T Schrefl, Hans Peter Stimming, Norbert J MauserAbstract:We present a steepest descent energy minimization scheme for Micromagnetics. The method searches on a curve that lies on the sphere which keeps the magnitude of the magnetization vector constant. The step size is selected according to a modified Barzilai-Borwein method. Standard linear tetrahedral finite elements are used for space discretization. For the computation of static hysteresis loops the steepest descent minimizer is faster than a Landau-Lifshitz micromagnetic solver by more than a factor of two. The speed up on a graphic processor is 4.8 as compared to the fastest single-core CPU implementation.
Lukas Exl - One of the best experts on this subject based on the ideXlab platform.
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computational Micromagnetics with commics
Computer Physics Communications, 2020Co-Authors: Carlmartin Pfeiler, Lukas Exl, Norbert J Mauser, G Hrkac, Michele Ruggeri, Bernhard Stiftner, Matthias Hochsteger, Joachim Schoberl, Dirk PraetoriusAbstract:Abstract We present our open-source Python module Commics for the study of the magnetization dynamics in ferromagnetic materials via micromagnetic simulations. It implements state-of-the-art unconditionally convergent finite element methods for the numerical integration of the Landau–Lifshitz–Gilbert equation. The implementation is based on the multiphysics finite element software Netgen/NGSolve. The simulation scripts are written in Python, which leads to very readable code and direct access to extensive post-processing. Together with documentation and example scripts, the code is freely available on GitLab. Program summary Program title: Commics Program Files doi: http://dx.doi.org/10.17632/29wv9h78h7.1 Licensing provisions: GPLv3 Programming language: Python3 Nature of problem: Numerical integration of the Landau–Lifshitz–Gilbert equation in three space dimensions Solution method: Tangent plane scheme [1]: original first-order version, projection-free version, second-order version, efficient second-order IMEX version; Midpoint scheme [2]: original version, IMEX version; Magnetostatic Maxwell equations are treated by the hybrid FEM–BEM method [3] Additional comments including restrictions and unusual features: An installation of the finite element software Netgen/NGSolve and an installation of the boundary element library BEM++ are required. References [1] F. Alouges. A new finite element scheme for Landau–Lifchitz equations. Discrete Contin. Dyn. Syst. Ser. S, 1(2):187–196, 2008. [2] S. Bartels and A. Prohl. Convergence of an implicit finite element method for the Landau–Lifshitz–Gilbert equation. SIAM J. Numer. Anal., 44(4):1405–1419, 2006. [3] D. R. Fredkin and T. R. Koehler. Hybrid method for computing demagnetization fields. IEEE Trans. Magn., 26(2):415–417, 1990.
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labonte s method revisited an effective steepest descent method for micromagnetic energy minimization
Journal of Applied Physics, 2014Co-Authors: Lukas Exl, Simon Bance, Franz Reichel, T Schrefl, Hans Peter Stimming, Norbert J MauserAbstract:We present a steepest descent energy minimization scheme for Micromagnetics. The method searches on a curve that lies on the sphere which keeps the magnitude of the magnetization vector constant. The step size is selected according to a modified Barzilai-Borwein method. Standard linear tetrahedral finite elements are used for space discretization. For the computation of quasistatic hysteresis loops, the steepest descent minimizer is faster than a Landau-Lifshitz micromagnetic solver by more than a factor of two. The speed up on a graphic processor is 4.8 as compared to the fastest single-core central processing unit (CPU) implementation.
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labonte s method revisited an effective steepest descent method for micromagnetic energy minimization
arXiv: Computational Physics, 2013Co-Authors: Lukas Exl, Simon Bance, Franz Reichel, T Schrefl, Hans Peter Stimming, Norbert J MauserAbstract:We present a steepest descent energy minimization scheme for Micromagnetics. The method searches on a curve that lies on the sphere which keeps the magnitude of the magnetization vector constant. The step size is selected according to a modified Barzilai-Borwein method. Standard linear tetrahedral finite elements are used for space discretization. For the computation of static hysteresis loops the steepest descent minimizer is faster than a Landau-Lifshitz micromagnetic solver by more than a factor of two. The speed up on a graphic processor is 4.8 as compared to the fastest single-core CPU implementation.
Jiangang Zhu - One of the best experts on this subject based on the ideXlab platform.
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1. Micromagnetic modeling of domain structures in magnetic thin films
Experimental Methods in the Physical Sciences, 2001Co-Authors: Jiangang ZhuAbstract:Publisher Summary This chapter reviews the theory of micromagnetic modeling along with computation methods and presents the comparisons of various simulation results with experimental observations. The chapter focuses on the relation between observations and modeling results. The examples of simulated domain structures in various patterned thin film elements are illustrated in the chapter. An example of utilizing micromagnetic modeling to aid the engineering of thin film microstructure is presented in the chapter. Micromagnetic modeling is a powerful tool for understanding the magnetization processes in magnetic films and thin film devices, thereby providing guidelines to material microstructure engineering and device design. However, experimental verifications are often needed to ensure the validity of the modeling results. Magnetic imaging techniques, such as magnetic force microscopy and various transmission electron microscopy techniques, not only can provide direct understanding of the micromagnetic behavior but also help provide comparisons for either verifying a modeling study or for changing or revising the model. The dynamic approach in micromagnetic modeling is sometimes critical. The inclusion of gyromagnetic motion is often absolutely necessary.
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Micromagnetics of small size patterned exchange biased permalloy film elements invited
Journal of Applied Physics, 1997Co-Authors: Jiangang Zhu, Youfeng Zheng, Xiangdong LinAbstract:In this article, we present a study on the Micromagnetics of exchange biased Permalloy films. Specifically, by combining magnetic force microscopy with micromagnetic modeling simulation, the magnetization reversal processes in exchange biased Permalloy films were studied. The bilayer films were lithographically patterned into micrometer scale rectangular elements. It is shown that the micromagnetic simulations accurately predict domain configurations during magnetization reversal of the exchange biased Permalloy film elements and provide detailed magnetization distributions and transient dynamic magnetization configurations that could not yet be obtained experimentally. The study found that, for both NiO/NiFe and FeMn/NiFe systems, the exchange bias field measured on individual patterned micrometer scale bilayer film elements can be significantly larger than that measured on the sheet film sample.
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Micromagnetic Modeling: Theory and Applications in Magnetic Thin Films.
MRS Bulletin, 1995Co-Authors: Jiangang ZhuAbstract:Micromagnetic theory concerns detailed magnetization configurations and the magnetization-reversal processes in a ferromagnetic system. By combining the original micromagnetic theory with a dynamic description of magnetization orientations, one can simulate complete magnetization processes and calculate important properties such as magnetic hysteresis and magnetic switching dynamics. Not only can micromagnetic simulation predict complex magnetic-domain configurations in a ferromagnetic system, it also can generate transient pictures showing how a complex domain configuration forms. Very important among these systems are ferromagnetic thin films, particularly those used in sensors and recording devices. Micromagnetic modeling not only has enriched our understanding of existing magnetic films but has also been used to successfully predict the magnetic properties of new film microstructures created for particular applications.In this article, a brief introduction of micromagnetic-modeling theory will be given. Modeling of soft and hard magnetic films will be discussed separately through two examples illustrating the essence of micromagnetic-magnetization processes in these films.
Jeanchristophe Toussaint - One of the best experts on this subject based on the ideXlab platform.
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chiral nature of magnetic monopoles in artificial spin ice
arXiv: Mesoscale and Nanoscale Physics, 2014Co-Authors: Nicolas Rougemaille, F Montaigne, Benjamin Canals, M Hehn, H Riahi, D Lacour, Jeanchristophe ToussaintAbstract:Micromagnetic properties of monopoles in artificial kagome spin ice systems are investigated using numerical simulations. We show that Micromagnetics brings additional complexity into the physics of these monopoles that is, by essence, absent in spin models: besides a fractionalized classical magnetic charge, monopoles in the artificial kagome ice are chiral at remanence. Our simulations predict that the chirality of these monopoles can be controlled without altering their charge state. This chirality breaks the vertex symmetry and triggers a directional motion of the monopole under an applied magnetic field. Our results also show that the choice of the geometrical features of the lattice can be used to turn on and off this chirality, thus allowing the investigation of chiral and achiral monopoles.
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chiral nature of magnetic monopoles in artificial spin ice
New Journal of Physics, 2013Co-Authors: Nicolas Rougemaille, F Montaigne, Benjamin Canals, M Hehn, H Riahi, D Lacour, Jeanchristophe ToussaintAbstract:Micromagnetic properties of monopoles in artificial kagome spin ice systems are investigated using numerical simulations. We show that Micromagnetics brings additional complexity into the physics of these monopoles that is, by essence, absent in spin models: in addition to a fractionalized classical magnetic charge, monopoles in the artificial kagome ice are chiral at remanence. Our simulations predict that the chirality of these monopoles can be controlled without altering their charge state. This chirality breaks the vertex symmetry and triggers a directional motion of the monopole under an applied magnetic field. Our results also show that the choice of the geometrical features of the lattice can be used to turn on and off this chirality, thus allowing the investigation of chiral and achiral monopoles.
Dieter Suess - One of the best experts on this subject based on the ideXlab platform.
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a full fledged micromagnetic code in fewer than 70 lines of numpy
Journal of Magnetism and Magnetic Materials, 2015Co-Authors: Claas Abert, Florian Bruckner, Christoph Vogler, Roman Windl, Raphael Thanhoffer, Dieter SuessAbstract:Abstract We present a complete micromagnetic finite-difference code in fewer than 70 lines of Python. The code makes a large use of the NumPy library and computes the exchange field by finite differences and the demagnetization field with a fast convolution algorithm. Since the magnetization in finite-difference Micromagnetics is represented by a multi-dimensional array and the NumPy library features a rich interface for this data structure, the code we present is an ideal starting point for the development of novel algorithms.
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numerical methods in Micromagnetics finite element method
Handbook of Magnetism and Advanced Magnetic Materials, 2007Co-Authors: T Schrefl, Dieter Suess, Simon Bance, G Hrkac, Otmar Ertl, J FidlerAbstract:Micromagnetic simulations provide guidelines for the development of composite magnetic materials and magnetic devices. The granular structure of a material and the magnetic interactions between the different magnetic parts of a device can be easily taken into account by the finite element method and the boundary element method, respectively. The finite element equations are derived for the calculation of the magnetostatic field. Similarly, it is shown how the total energy of a magnetic system can be computed by matrix-vector operations. Efficient methods for calculating equilibrium magnetic states and the simulation of the dynamic response of a magnetic material to a time varying external field are discussed. Numerical schemes for the simulation of magnetization dynamics in systems involving moving parts are introduced. The numerical methods are demonstrated by showing results of perpendicular magnetic recording simulation on composite media. Keywords: Micromagnetics; finite element method; magnetic recording
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Micromagnetic modelling and magnetization processes
Journal of Magnetism and Magnetic Materials, 2004Co-Authors: Josef Fidler, Werner Scholz, Thomas Schrefl, Dieter Suess, R. Dittrich, M. KirschnerAbstract:Micromagnetics is a continuum theory to describe magnetization processes on a length scale which is large enough to replace the atomic spins by a continuous magnetization vector and small enough to resolve the magnetization transition inside a domain wall. Depending on the magnetocrystalline anisotropy the characteristic length scale, the domain wall width or the minimum discretization size, is in the order of several nanometres to micrometres. Typical examples for numerical micromagnetic simulations are shown, where the role of a granular microstructure and precipitates on hysteresis properties is significant, such as in FePt nanocrystals, granular CoCrPtX thin films for longitudinal magnetic recording and modern bulk rare earth permanent magnets.
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Scalable parallel micromagnetic solvers for magnetic nanostructures
Computational Materials Science, 2003Co-Authors: Werner Scholz, Josef Fidler, Thomas Schrefl, Dieter Suess, R. Dittrich, H. Forster, V. TsiantosAbstract:A parallel finite element Micromagnetics package has been implemented, that is highly scalable, easily portable and combines different solvers for the micromagnetic equations. The implementation is based on the standard Galerkin discretization on tetrahedral meshes with linear basis functions. A static energy minimization, a dynamic time integration, and the nudged elastic band method have been implemented. The details of the implementation and some aspects of the optimization are discussed and timing and speedup results are given. Nucleation and magnetization reversal processes in permalloy nanodots are investigated with this Micromagnetics package.
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Scalable Parallel Micromagnetic Solvers for
2003Co-Authors: Werner Scholz, Josef Fidler, Thomas Schrefl, Dieter Suess, R. Dittrich, H. Forster, V. TsiantosAbstract:A parallel finite element Micromagnetics package has been implemented, that is highly scalable, easily portable and combines dierent solvers for the micromagnetic equations. The implementation is based on the standard Galerkin discretization on tetrahedral meshes with linear basis functions. A static energy minimization, a dynamic time integration, and the nudged elastic band method have been implemented. The details of the implementation and some aspects of the optimization are discussed and timing and speedup results are given. Nucleation and magnetization reversal processes in permalloy nanodots are investigated with this Micromagnetics package.