Magnetization reversal processes of isotropic permanent magnets with various inter-grain exchange interactions

Tsukahara, Hiroshi; Iwano, Kaoru; Mitsumata, Chiharu; Ishikawa, Tadashi; Ono, Kanta

doi:10.1063/1.4976950

Cited by 5 publications

(4 citation statements)

References 17 publications

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“…In nonlinear conjugate gradient methods the search directions are linear combinations of vectors perpendicular to the magnetization (the current projected gradient and the previous search directions initially being the projected gradient). Instead of updating and normalization, the vectors m i might also be rotated by an angle α |d i | [66] or a norm conserving semi-implicit update rule [67] may be applied. The right-hand side of equation ( 22) follows from the vector identity a×(b…”

Section: Energy Minimizationmentioning

confidence: 99%

“…In turn, fast reversal reduces the total computation time. This is the motivation for using a damping parameter α = 1 for simulation of magnetization reversal in permanent magnets [66,72] by numerical integration of equation (25). Several public domain micromagnetic software tools use solvers for the numerical solution of equation ( 25) based on the adaptive Euler methods [73], Runge-Kutta schemes [62], backward-differentiation methods [74], and preconditioned implicit solvers [75].…”

Section: Time Integrationmentioning

confidence: 99%

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Micromagnetics of rare-earth efficient permanent magnets

Fischbacher

Kovacs

Gusenbauer

et al. 2018

J. Phys. D: Appl. Phys.

100

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The development of permanent magnets containing less or no rareearth elements is linked to profound knowledge of the coercivity mechanism. Prerequisites for a promising permanent magnet material are a high spontaneous magnetization and a sufficiently high magnetic anisotropy. In addition to the intrinsic magnetic properties the microstructure of the magnet plays a significant role in establishing coercivity. The influence of the microstructure on coercivity, remanence, and energy density product can be understood by using micromagnetic simulations. With advances in computer hardware and numerical methods, hysteresis curves of magnets can be computed quickly so that the simulations can readily provide guidance for the development of permanent magnets. The potential of rare-earth reduced and free permanent magnets is investigated using micromagnetic simulations. The results show excellent hard magnetic properties can be achieved in grain boundary engineered NdFeB, rare-earth magnets with a ThMn 12 structure, Co-based nano-wires, and L1 0 -FeNi provided that the magnet's microstructure is optimized.

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Section: Energy Minimizationmentioning

confidence: 99%

Section: Time Integrationmentioning

confidence: 99%

Micromagnetics of rare-earth efficient permanent magnets

Fischbacher

Kovacs

Gusenbauer

et al. 2018

J. Phys. D: Appl. Phys.

100

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show abstract

“…In this study, we investigated magnetization reversal inside a permanent magnet during the demagnetization process and the effects of the microstructure of the permanent magnet on the generation of magnetic nucleation using a large-scale micromagnetics simulation based on the Landau-Lifshitz-Gilbert (LLG) equation [32][33][34][35][36][37][38][39] . When the external field approaches the coercivity of the permanent magnet, magnetization reversal is initiated in some grains; the density of the grains undergoing nucleation is small.…”

Section: Introductionmentioning

confidence: 99%

Relationship between magnetic nucleation and the microstructure of a hot-deformed permanent magnet: micromagnetic simulation

et al. 2020

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The grains initiating magnetization reversal in the microstructure of a hot-deformed permanent magnet have been identified in this study by performing micromagnetic simulations based on the Landau-Lifshitz-Gilbert equation. Hotdeformed permanent magnets comprise tabular grains, the easy-axis orientations of which are inclined with respect to the nominal easy axis of the permanent magnet. In the simulation model, the grains complexly overlap, similar to in actual permanent magnets. We analyze the simulation results considering grain overlap and the easy-axis tilt angles of the grains. The initiation of magnetic nucleation requires a high concentration of grains with large easy-axis tilt angles. We clarify the magnetic-nucleation process and provide a method to enhance the performance of permanent magnets by avoiding a high concentration of grains with large easy-axis tilt angles.

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“…[12][13][14][15] We can perform large-scale micromagnetic simulations employing more than 0.1 billion calculation cells using supercomputing systems. Hence, we can accurately simulate a Author to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Effect of grain boundary phase on the magnetization reversal process of nanocrystalline magnet using large-scale micromagnetic simulation

et al. 2018

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We investigated the effects of grain boundary phases on magnetization reversal in permanent magnets by performing large-scale micromagnetic simulations based on Landau–Lifshitz–Gilbert equation under a periodic boundary. We considered planar grain boundary phases parallel and perpendicular to an easy axis of the permanent magnet and assumed the saturation magnetization and exchange stiffness constant of the grain boundary phase to be 10% and 1%, respectively, for Nd2Fe14B grains. The grain boundary phase parallel to the easy axis effectively inhibits propagation of magnetization reversal. In contrast, the domain wall moves across the grain boundary perpendicular to the easy axis. These properties of the domain wall motion are explained by dipole interaction, which stabilizes the antiparallel magnetic configuration in the direction perpendicular to the magnetization orientation. On the other hand, the magnetization is aligned in the same direction by the dipole interaction parallel to the magnetization orientation. This anisotropy of the effect of the grain boundary phase shows that improvement of the grain boundary phase perpendicular to the easy axis effectively enhances the coercivity of permanent magnets.

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Magnetization reversal processes of isotropic permanent magnets with various inter-grain exchange interactions

Cited by 5 publications

References 17 publications

Micromagnetics of rare-earth efficient permanent magnets

Micromagnetics of rare-earth efficient permanent magnets

Relationship between magnetic nucleation and the microstructure of a hot-deformed permanent magnet: micromagnetic simulation

Effect of grain boundary phase on the magnetization reversal process of nanocrystalline magnet using large-scale micromagnetic simulation

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