Micromagnetic simulations with periodic boundary conditions: Hard-soft nanocomposites

Wysocki, Aleksander L.; Antropov, Vladimir

doi:10.1016/j.jmmm.2016.11.128

Cited by 22 publications

(16 citation statements)

References 93 publications

(83 reference statements)

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“…Solutions have been proposed for 1D and 2D problems 8,9 , however an extension to 3D is not possible since the occurring sums are not absolutely convergent. Using point-dipoles instead of finite magnetized cubes seems to overcome this limitation and allows true 3D periodic boundary conditions 10 . In contrast to true PBCs which require an infinite summation, some codes use pseudo PBCs where the summation is truncated after a finite number of periodic images 2,3 .…”

Section: Strayfield Calculation For Micromagnetic Simulations Using T...mentioning

confidence: 99%

Strayfield calculation for micromagnetic simulations using true periodic boundary conditions

Bruckner

Ducevic

Heistracher

et al. 2021

Sci Rep

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We present methods for calculating the strayfield in finite element and finite difference micromagnetic simulations using true periodic boundary conditions. In contrast to pseudo periodic boundary conditions, which are widely used in micromagnetic codes, the presented methods eliminate the shape anisotropy originating from the outer boundary. This is a crucial feature when studying the influence of the microstructure on the performance of composite materials, which is demonstrated by hysteresis calculations of soft magnetic structures that are operated in a closed magnetic loop configuration. The applied differential formulation is perfectly suited for the application of true periodic boundary conditions. The finite difference equations can be solved by a highly efficient Fast Fourier Transform method.

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Section: Strayfield Calculation For Micromagnetic Simulations Using T...mentioning

confidence: 99%

Strayfield calculation for micromagnetic simulations using true periodic boundary conditions

Bruckner

Ducevic

Heistracher

et al. 2021

Sci Rep

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show abstract

“…To realize stronger coercivities at higher temperatures, it is necessary to study the effect of grain boundaries on the coercivity. For this purpose, a prototype hard-soft-hard magnet model, in which outer hard magnets are in contact with a middle soft magnet, has been intensively studied [45][46][47][48][49][50]93,94]. This model captures the essence of nucleation and depinning in inhomogeneous systems, and has been frequently used in analyses of the phenomena in various experimental and theoretical studies of magnetic materials [42,95] including GMR sensors [96].…”

Section: Sandwich Structurementioning

confidence: 99%

Atomistic theory of thermally activated magnetization processes in Nd₂Fe₁₄B permanent magnet

Miyashita

Nishino

Toga

et al. 2021

Science and Technology of Advanced Materials

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For the practical use of magnets, particularly at high temperatures, the temperature dependence of magnetic properties is an important ingredient. To study the temperature dependence, methods of treating the thermal fluctuation causing the so-called activation phenomena must be established. To study finite-temperature properties quantitatively, we need atomistic energy information to calculate the canonical distribution. In the present review, we report our recent studies on the thermal properties of the Nd 2 Fe 14 B magnet and the methods of studying them. We first propose an atomistic Hamiltonian and show various thermodynamic properties, e.g., the temperature dependences of the magnetization showing a spin reorientation transition, the magnetic anisotropy energy, the domain wall profiles, the anisotropy of the exchange stiffness constant, and the spectrum of ferromagnetic resonance. The effects of the dipole-dipole interaction (DDI) in large grains are also presented. In addition to these equilibrium properties, we also study coercivity, which is the most important issue for magnets. The temperature dependence of the coercivity of a single grain was studied using the stochastic Landau-Lifshitz-Gilbert equation and also by the analysis of the free energy landscape, which was obtained by Monte Carlo simulation. It was found that the upper limit of coercivity at room temperature is about 3T, which is significantly lower than the so-called theoretical coercivity given by a simple coherent rotation model. The coercivity of a polycrystalline magnet, i.e., an ensemble of grains, is expected to be reduced further by the effects of the grain boundary phase, which is also studied. Surface nucleation is a key ingredient in the domain wall depinning process. Finally, we study the effect of DDI among grains and also discuss the distribution of properties of grains from the viewpoint of first order reversal curve.

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“…In addition, the blocks interact via the magnetostatic interaction that is described using the Ewald technique as detailed in Ref. 77. In a manner similar to the approach in Ref.…”

Section: B Multiscale Modelingmentioning

confidence: 99%

Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior in theTa-,Cu-, andFe-Substituted
Lamichhane
¹
,
Onyszczak
²
,
Palasyuk
³

et al. 2019
Phys. Rev. Applied
Self Cite

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To reduce material and processing costs of commercial permanent magnets and to attempt to fill the empty niche of energy products, 10-20 MGOe, between low-flux (ferrites, alnico) and highflux (Nd2Fe14B-and SmCo5-type) magnets, we report synthesis, structure, magnetic properties and modeling of Ta, Cu and Fe substituted CeCo5. Using a self-flux technique, we grew single crystals of I-Ce15.1Ta1.0Co74.4Cu9.5, II-Ce16.3Ta0.6Co68.9Cu14.2, III-Ce15.7Ta0.6Co67.8Cu15.9, IV-Ce16.3Ta0.3Co61.7Cu21.7 and V-Ce14.3Ta1.0Co62.0Fe12.3Cu10.4. X-ray diffraction analysis (XRD) showed that these materials retain a CaCu5 substructure and incorporate small amounts of Ta in the form of "dumb-bells", filling the 2e crystallographic sites within the 1D hexagonal channel with the 1a Ce site, whereas Co, Cu and Fe are statistically distributed among the 2c and 3g crystallographic sites. Scanning electron microscopy, energy dispersive X-ray spectroscopy (SEM-EDS) and scanning transmission electron microscopy (STEM) examinations provided strong evidence of the single-phase nature of the as-grown crystals, even though they readily exhibited significant magnetic coercivities of ∼1.6-∼1.8 kOe caused by Co-enriched, nano-sized, structural defects and faults that can serve as pinning sites. Heat treatments at 1040 • C for 10 h and a hardening at 400 • C for 4 h lead to the formation of a so-called "composite crystal" with a bimodal microstructure that consists of a Tapoor matrix and Ta-rich laminal precipitates. Formation of the "composite crystal" during the heat treatment creates a 3D array of extended defects within a primarily single grain single crystal, which greatly improves its magnetic characteristics. Possible causes of the formation of the "composite crystal" may be associated with Ta atoms leaving matrix interstices at lower temperatures and/or matrix degradation induced by decreased miscibility at lower temperatures. Fe strongly improves both the Curie temperature and magnetization of the system resulting in (BH)max.≈13 MGOe at room temperature.

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Micromagnetic simulations with periodic boundary conditions: Hard-soft nanocomposites

Cited by 22 publications

References 93 publications

Strayfield calculation for micromagnetic simulations using true periodic boundary conditions

Strayfield calculation for micromagnetic simulations using true periodic boundary conditions

Atomistic theory of thermally activated magnetization processes in Nd₂Fe₁₄B permanent magnet

Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior in theTa-,Cu-, andFe-Substituted
Lamichhane
¹
,
Onyszczak
²
,
Palasyuk
³

et al. 2019
Phys. Rev. Applied
Self Cite

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Micromagnetic simulations with periodic boundary conditions: Hard-soft nanocomposites

Cited by 22 publications

References 93 publications

Strayfield calculation for micromagnetic simulations using true periodic boundary conditions

Strayfield calculation for micromagnetic simulations using true periodic boundary conditions

Atomistic theory of thermally activated magnetization processes in Nd2Fe14B permanent magnet

Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior in theTa-,Cu-, andFe-SubstitutedLamichhane1, Onyszczak2, Palasyuk3 et al. 2019Phys. Rev. AppliedSelf Cite

Contact Info

Product

Resources

About

Atomistic theory of thermally activated magnetization processes in Nd₂Fe₁₄B permanent magnet

Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior in theTa-,Cu-, andFe-Substituted
Lamichhane
¹
,
Onyszczak
²
,
Palasyuk
³

et al. 2019
Phys. Rev. Applied
Self Cite