Journal Description
Magnetism
Magnetism
is an international, peer-reviewed, open access journal on science and technology for all original researches on magnetism and related fields, published quarterly online by MDPI. The UK Magnetics Society (UKMagSoc) is affiliated with Magnetism and their members receive discounts on the article processing charges.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 34.7 days after submission; acceptance to publication is undertaken in 8.9 days (median values for papers published in this journal in the first half of 2024).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
- Magnetism is a companion journal of Electronics.
Latest Articles
Can We Still Find an Ideal Memristor?
Magnetism 2024, 4(3), 200-208; https://doi.org/10.3390/magnetism4030014 - 16 Jul 2024
Abstract
In 1971, Chua defined an ideal memristor that links magnetic flux φ and electric charge q. In a magnetic lump with a current-carrying conductor, we found that the direct interaction between physical magnetic flux φ and physical electric charge q is memristive by
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In 1971, Chua defined an ideal memristor that links magnetic flux φ and electric charge q. In a magnetic lump with a current-carrying conductor, we found that the direct interaction between physical magnetic flux φ and physical electric charge q is memristive by nature in terms of a time-invariant φ-q curve being nonlinear, continuously differentiable and strictly monotonically increasing. Although we succeeded in demonstrating that the “ideal/real/perfect/… memristor” needs magnetism, the structure still suffers from two serious limitations: 1. a parasitic “inductor” effect and 2. bistability and dynamic sweep of a continuous resistance range. Then, we discussed how to overcome these two limitations to make a fully functioning ideal memristor with multiple or an infinite number of stable states and no parasitic inductance. We then gave a number of innovations to the current memristor structure, such as an “open” structure, nanoscale size, magnetic materials with cubic anisotropy (or even isotropy) and sequential switching of the magnetic domains. Contrary to the conjecture that “an ideal memristor may not exist or may be a purely mathematical concept”, we remain optimistic that an ideal memristor will be discovered in nature or will be made in the laboratory. Our finding of the memristive flux–charge interaction may advance the development and application of the memristor technology.
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(This article belongs to the Special Issue Mathematical Modelling and Physical Applications of Magnetic Systems)
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Open AccessArticle
Analytical Solutions of Symmetric Isotropic Spin Clusters Using Spin and Point Group Projectors
by
Shadan Ghassemi Tabrizi and Thomas D. Kühne
Magnetism 2024, 4(3), 183-199; https://doi.org/10.3390/magnetism4030013 - 5 Jul 2024
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Spin models like the Heisenberg Hamiltonian effectively describe the interactions of open-shell transition-metal ions on a lattice and can account for various properties of magnetic solids and molecules. Numerical methods are usually required to find exact or approximate eigenstates, but for small clusters
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Spin models like the Heisenberg Hamiltonian effectively describe the interactions of open-shell transition-metal ions on a lattice and can account for various properties of magnetic solids and molecules. Numerical methods are usually required to find exact or approximate eigenstates, but for small clusters with spatial symmetry, analytical solutions exist, and a few Heisenberg systems have been solved in closed form. This paper presents a simple, generally applicable approach to analytically solve isotropic spin clusters, based on adapting the basis to both total spin and point group symmetry to factor the Hamiltonian matrix into sufficiently small blocks. We demonstrate applications to small rings and polyhedra, some of which are straightforward to solve by successive spin-coupling for Heisenberg terms only; additional interactions, such as biquadratic exchange or multi-center terms necessitate symmetry adaptation.
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Open AccessFeature PaperArticle
An Update to The Demagnetizing Factor Dataset Calculated for The General Ellipsoid by Osborn
by
László F. Kiss and Imre Bakonyi
Magnetism 2024, 4(3), 173-182; https://doi.org/10.3390/magnetism4030012 - 30 Jun 2024
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The exact formulae for calculating the demagnetizing factors of a general ellipsoid along the three main axes a ≥ b ≥ c have been long known. According to these formulae, the demagnetizing factors depend only on the axial ratios b/a and
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The exact formulae for calculating the demagnetizing factors of a general ellipsoid along the three main axes a ≥ b ≥ c have been long known. According to these formulae, the demagnetizing factors depend only on the axial ratios b/a and c/a. Although the calculation of the demagnetizing factors is a straightforward task, the calculation itself is not a simple one. Therefore, tabular and graphical representations of these demagnetizing factor data have also been presented which can then be used for approximating the demagnetizing factors of a rectangular ferromagnetic slab with the same axial ratios. It turned out in our recent study, however, that, in some ranges of axial ratios (e.g., for very small c/a values), the available tables and graphs do not provide sufficient resolution for obtaining the demagnetizing factors with reasonable accuracy. It was decided to calculate these missing values, and they are presented here in both tabular and graphical form by giving instructions for how to obtain conveniently further interpolated data. In addition, the previous and current demagnetizing factor data have been replotted and fitted to a polynomial function with high accuracy. The functional form of these fitting polynomials is presented in a table for the whole range of the axial ratios b/a and c/a. By graphically displaying these functions, one can obtain, in a relatively simple manner, the demagnetizing factors of a general ellipsoid with known axial ratios without the need to directly calculate through the exact formulae. This may be helpful in obtaining a quick estimate for the demagnetizing factors of any rectangular ferromagnetic slab of interest.
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Open AccessArticle
The Influence of the Design and Technological Parameters of Polymer-Based Multipolar Magnets with SrFeO Hard Magnetic Filler on the Residual Magnetic Properties
by
Uta Rösel and Dietmar Drummer
Magnetism 2024, 4(3), 157-172; https://doi.org/10.3390/magnetism4030011 - 28 Jun 2024
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Multipolar bonded magnets based on a thermoset matrix provide the opportunity to expand the applications of bonded magnets, especially within the drive technology industry, in terms of the high thermal and chemical resistance, along with a higher utilisation of the magnetic potential. To
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Multipolar bonded magnets based on a thermoset matrix provide the opportunity to expand the applications of bonded magnets, especially within the drive technology industry, in terms of the high thermal and chemical resistance, along with a higher utilisation of the magnetic potential. To realize the application of polymer bonded magnets based on thermosets within the drive technology industry, general design parameters in terms of the material, the process parameters, and the tool concept are needed. These allow for a fundamental realization of multipolar bonded magnets with complex geometries in drive technologies, based on thermosets as the matrix material. This paper investigates the impact of the material (matrix material and filler grade), the process conditions (holding pressure (ph) and heating time (th)), and the tool concept (gating position and system, sleeve material, pole division, and sample thickness) on the magnetic properties in terms of the remanence (BR) and the deviation (Δs) of the pole division, as well as the orientation of the fillers in the middle of the pole and at the pole pitch. For each parameter, an optimised value is derived. In the majority of the cases, this value is equal in terms of the magnetic properties and the orientation. In terms of the sleeve material and the sample thickness, the ideal value differs between the two criteria. Therefore, an optimised value for each criterion, as well as an overall value, is defined. In terms of the material, PF, along with a high filler grade; in terms of the process conditions, a high holding pressure (ph) and a low heating time (th); and in terms of the tool concept, a two-pinpoint gating system, located in the middle of the pole, a Ferro-Titanit-Cromoni sleeve material, a high pole division, as well as small sample thickness, should be selected to improve the properties of polymer bonded magnets based on thermosets.
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Open AccessReview
Additively Manufactured Alnico Permanent Magnet Materials—A Review
by
Saikumar Dussa, Sameehan S. Joshi, Shashank Sharma, Karri Venkata Mani Krishna, Madhavan Radhakrishnan and Narendra B. Dahotre
Magnetism 2024, 4(2), 125-156; https://doi.org/10.3390/magnetism4020010 - 30 May 2024
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Additive manufacturing offers manufacturing flexibility for intricate components and also allows for precise control over the microstructure. This review paper explores the current state of the art in additive manufacturing techniques for Alnico permanent magnets, emphasizing the notable advantages and challenges associated with
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Additive manufacturing offers manufacturing flexibility for intricate components and also allows for precise control over the microstructure. This review paper explores the current state of the art in additive manufacturing techniques for Alnico permanent magnets, emphasizing the notable advantages and challenges associated with this innovative approach. Both the LPBF and L-DED processes have demonstrated promising results in fabricating Alnico with magnetic properties comparable with conventionally processed samples. The optimization of process parameters successfully reduced porosity and cracking in the LPBF processing of Alnico. The review further explored the significance of additive manufacturing process parameter optimization in managing the temperature gradient and solidification rate for a desired microstructure and enhanced magnetic properties. Other potential additive manufacturing methods suitable for the fabrication of Alnico were discussed, along with the challenges associated with the process. The insights provided also highlight how additive manufacturing holds the potential to replace post-processing techniques like solutionization, magnetic annealing, and tempering often necessary in Alnico production.
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Open AccessArticle
The Influence of Blood and Serum Microenvironment on Spin-Labeled Magnetic Nanoparticles
by
Tomasz Kubiak
Magnetism 2024, 4(2), 114-124; https://doi.org/10.3390/magnetism4020009 - 10 May 2024
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The investigation and clarification of the properties of surface-functionalized superparamagnetic nanoparticles in a biological environment are key challenges prior to their medical applications. In the present work, electron paramagnetic resonance spectroscopy (EPR) combined with the spin labeling technique was utilized to better understand
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The investigation and clarification of the properties of surface-functionalized superparamagnetic nanoparticles in a biological environment are key challenges prior to their medical applications. In the present work, electron paramagnetic resonance spectroscopy (EPR) combined with the spin labeling technique was utilized to better understand the behavior of nitroxides attached to magnetite nanoparticles dispersed in body fluid. EPR spectra of spin-labeled, silane-coated Fe3O4 nanoparticles in human serum and whole blood were recorded and analyzed for both room- and low-temperature values. In all cases, the obtained EPR signal consisted of a broad line from magnetite cores and a characteristic signal from the attached 4-Amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO). Even for liquid samples, the anisotropic components of magnetic tensors did not fully average out, which was reflected in the differences in the intensity of three narrow hyperfine lines from nitroxide. At 230 K the irregular slow-motion signal from the attached radical was also simulated using the EasySpin toolbox, which allowed to determine the parameters related to magnetic tensors and the dynamics of the spin label. The study showed that the anisotropy of the motion of the spin label 4-amino-TEMPO reflects its interactions with the surrounding medium and the manner of the attachment of the nitroxide to the surface of nanoparticles.
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Open AccessArticle
Magnetoresistive Evidence of Degeneracy in Nanomagnets Obtained by Electrodeposition Technique
by
Lara B. Oliveira, Teonis S. Paiva, Hamilton A. Teixeira and Clodoaldo I. L. de Araujo
Magnetism 2024, 4(2), 104-113; https://doi.org/10.3390/magnetism4020008 - 7 Apr 2024
Cited by 1
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Inspired in pyrochlore materials presenting residual entropy and featuring collective excitation behaving like emergent monopoles, geometrically frustrated arrays of nanomagnets, denominated artificial spin ices (ASIs), were proposed as an interesting platform to investigate such excitation at room temperature. However, in such artificial systems,
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Inspired in pyrochlore materials presenting residual entropy and featuring collective excitation behaving like emergent monopoles, geometrically frustrated arrays of nanomagnets, denominated artificial spin ices (ASIs), were proposed as an interesting platform to investigate such excitation at room temperature. However, in such artificial systems, emergent magnetic monopoles lack the same freedom present their natural counterpart, once energetic strings connecting opposite magnetic charges arise. In this work, we aim to experimentally investigate the proposed degeneracy obtained in connected square arrays of ASIs, a characteristic that allows a reduction in the string connecting monopole–antimonopole pairs in regular non-connected ASIs and could represent an important development for technological applications of connected nanomagnets. As in general those systems are developed by nanofabrication processes involving expensive and time-consuming physical vapour deposition techniques, we also present a new nanofabrication route using an electrodeposition technique for permalloy growth in different lattice geometries as an alternative for fast and low-cost ASI system production.
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Open AccessArticle
Chiral Modulations in Non-Heisenberg Models of Non-Centrosymmetric Magnets Near the Ordering Temperatures
by
Andrey O. Leonov
Magnetism 2024, 4(2), 91-103; https://doi.org/10.3390/magnetism4020007 - 1 Apr 2024
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The structure of skyrmion and spiral solutions, investigated within the phenomenological Dzyaloshinskii model of chiral magnets near the ordering temperatures, is characterized by the strong interplay between longitudinal and angular order parameters, which may be responsible for experimentally observed precursor effects. Within the
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The structure of skyrmion and spiral solutions, investigated within the phenomenological Dzyaloshinskii model of chiral magnets near the ordering temperatures, is characterized by the strong interplay between longitudinal and angular order parameters, which may be responsible for experimentally observed precursor effects. Within the precursor regions, additional effects, such as pressure, electric fields, chemical doping, uniaxial strains and/or magnetocrystalline anisotropies, modify the energetic landscape and may even lead to the stability of such exotic phases as a square staggered lattice of half-skyrmions, the internal structure of which employs the concept of the “soft” modulus and contains points with zero modulus value. Here, we additionally alter the stiffness of the magnetization modulus to favor one- and two-dimensional modulated states with large modulations of the order parameter magnitude. The computed phase diagram, which omits any additional effects, exhibits stability pockets with a square half-skyrmion lattice, a hexagonal skyrmion lattice with the magnetization in the center of the cells parallel to the applied magnetic field, and helicoids with propagation transverse to the field, i.e., those phases in which the notion of localized defects is replaced by the picture of a smooth but more complex tiling of space. We note that the results can be adapted to metallic glasses, in which the energy contributions are the same and originate from the inherent frustration in the models, and chiral liquid crystals with a different ratio of elastic constants.
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Open AccessArticle
Wideband Millimeter-Wave Perforated Cylindrical Dielectric Resonator Antenna Configuration
by
Waled Albakosh, Rawad Asfour, Tarek S. Abdou, Yas Khalil and Salam K. Khamas
Magnetism 2024, 4(1), 73-90; https://doi.org/10.3390/magnetism4010006 - 18 Mar 2024
Cited by 1
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This article delves into the capabilities of 3D-printed millimeter-wave (mmWave) layered cylindrical dielectric resonator antennas (CDRAs). The proposed design yielded promising results, boasting a remarkable 53% impedance bandwidth spanning the frequency spectrum from 18 to 34 GHz. Furthermore, the axial ratio (AR) bandwidth
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This article delves into the capabilities of 3D-printed millimeter-wave (mmWave) layered cylindrical dielectric resonator antennas (CDRAs). The proposed design yielded promising results, boasting a remarkable 53% impedance bandwidth spanning the frequency spectrum from 18 to 34 GHz. Furthermore, the axial ratio (AR) bandwidth achieved an impressive 17%, coupled with a maximum gain of 13.3 dBic. These notable results underscore the efficacy of the proposed design, positioning it as a viable solution for applications in Beyond 5G (B5G). A novel assembly technique was also investigated, employing additive manufacturing to seamlessly merge two layers with distinct dielectric constants into a singular layer. This innovative approach systematically eliminates the potential for air gaps between layers, enhancing the antenna’s overall performance. This approach exhibited potential, particularly in the performance of a millimeter-wave circularly polarized (CP) cylindrical DRA featuring a perforated coating layer. The synergy between measurements and simulations demonstrates a remarkable alignment, providing robust validation of the effectiveness of the proposed design.
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Open AccessArticle
Effect of In-Plane Magnetic Field on Skyrmions in a Centrosymmetric Triangular-Lattice System with Symmetric Anisotropic Exchange Interaction
by
Satoru Hayami
Magnetism 2024, 4(1), 54-72; https://doi.org/10.3390/magnetism4010005 - 18 Mar 2024
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We report our numerical results on the stability of the skyrmion crystal phase in an external magnetic field for both in-plane and out-of-plane directions in a centrosymmetric host. We analyze a spin model with the two-spin symmetric anisotropic exchange interaction that arises from
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We report our numerical results on the stability of the skyrmion crystal phase in an external magnetic field for both in-plane and out-of-plane directions in a centrosymmetric host. We analyze a spin model with the two-spin symmetric anisotropic exchange interaction that arises from relativistic spin–orbit coupling on a triangular lattice. By performing simulated annealing, we construct magnetic phase diagrams when the magnetic field is tilted from the out-of-plane field direction to the in-plane field direction. We find a different stability tendency of the skyrmion crystal phase according to the directions of the in-plane field, which provides a signal of the two-spin symmetric anisotropic exchange interaction for stabilizing the skyrmion crystal phase. Our results indicate that the mechanism of the skyrmion crystal phase triggered by the two-spin symmetric anisotropic exchange interaction can be experimentally tested by applying the in-plane magnetic field.
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Open AccessCommunication
Far-Field Spatial Response of Off-Diagonal GMI Wire Magnetometers. Application to Magnetic Field Sources Sensing
by
Julien Gasnier and Christophe Dolabdjian
Magnetism 2024, 4(1), 47-53; https://doi.org/10.3390/magnetism4010004 - 21 Feb 2024
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Studying the spatial response of a single-axis magnetometer could be the key parameter to optimize the ultimate performances of magnetic heads of detection. Indeed, the problem of non-orthogonality, misalignment, and 3D spatial response could be improved based on the knowledge of the 3D
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Studying the spatial response of a single-axis magnetometer could be the key parameter to optimize the ultimate performances of magnetic heads of detection. Indeed, the problem of non-orthogonality, misalignment, and 3D spatial response could be improved based on the knowledge of the 3D sensor spatial response. In that way, we have investigated the latter for our giant magneto-impedance (GMI) magnetometer, as a far-field pattern, by using a three-axis Helmholtz coil system. Firstly, we calibrate our device and secondly, we apply a specific 3D magnetic field to obtain this pattern. The latter helps to observe the directional or angular dependence of the sensor sensitivity versus the applied magnetic field, as we exemplified. The results confirm the excellent directivity of our off-diagonal GMI magnetometer. The evaluation of the associated error compared to an ideal vector magnetometer is also given and discussed.
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Open AccessArticle
Coexistence of Long-Range Magnetic Order and Magnetic Frustration of a Novel Two-Dimensional S = 1/2 Structure: Na2Cu3(SeO3)4
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Emily D. Williams, Keith M. Taddei, Kulugammana G. S. Ranmohotti, Narendirakumar Narayanan, Thomas Heitmann, Joseph W. Kolis and Liurukara D. Sanjeewa
Magnetism 2024, 4(1), 35-46; https://doi.org/10.3390/magnetism4010003 - 13 Feb 2024
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Novel quantum materials offer the opportunity to expand next-generation computers, high-precision sensors, and new energy technologies. Among the most important factors influencing the development of quantum materials research is the ability of inorganic and materials chemists to grow high-quality single crystals. Here, the
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Novel quantum materials offer the opportunity to expand next-generation computers, high-precision sensors, and new energy technologies. Among the most important factors influencing the development of quantum materials research is the ability of inorganic and materials chemists to grow high-quality single crystals. Here, the synthesis, structure characterization and magnetic properties of Na2Cu3(SeO3)4 are reported. It exhibits a novel two-dimensional (2D) structure with isolated layers of Cu nets. Single crystals of Na2Cu3(SeO3)4 were grown using a low-temperature hydrothermal method. Single-crystal X-ray diffraction reveals that Na2Cu3(SeO3)4 crystallizes in the monoclinic crystal system and has space group symmetry of P21/n (No.14) with a unit cell of a = 8.1704(4) Å, b = 5.1659(2) Å, c = 14.7406(6) Å, β = 100.86(2), V = 611.01(5) Å3 and Z = 2. Na2Cu3(SeO3)4 comprises a 2D Cu-O-Cu lattice containing two unique copper sites, a CuO6 octahedra and a CuO5 square pyramid. The SeO3 groups bridge the 2D Cu-O-Cu layers isolating the neighboring Cu-O-Cu layers, thereby enhancing their 2D nature. Magnetic properties were determined by measuring the magnetic susceptibility of an array of randomly oriented single crystals of Na2Cu3(SeO3)4. The temperature-dependent magnetic measurement shows an antiferromagnetic transition at TN = 4 K. These results suggest the fruitfulness of hydrothermal synthesis in achieving novel quantum materials and encourage future work on the chemistry of transition metal selenite.
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Open AccessArticle
Phase Diagram Mapping out the Complex Magnetic Structure of Single Crystals of (Gd, Er)B4 Solid Solutions
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Sueli H. Masunaga, Vagner B. Barbeta, Fábio Abud, Milton S. Torikachvili and Renato F. Jardim
Magnetism 2024, 4(1), 24-34; https://doi.org/10.3390/magnetism4010002 - 4 Feb 2024
Abstract
Measurements of specific heat and magnetization in single crystals were used to map out the magnetic phase diagram of Gd1−xErxB4 (x = 0.2 and 0.4) solid solutions along the c-axis. While GdB4 orders antiferromagnetically
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Measurements of specific heat and magnetization in single crystals were used to map out the magnetic phase diagram of Gd1−xErxB4 (x = 0.2 and 0.4) solid solutions along the c-axis. While GdB4 orders antiferromagnetically (AF) at 41.7 K, with the easy plane of magnetization oriented perpendicularly to the c-axis, ErB4 displays AF ordering below 15.4 K, with the easy axis along c. Therefore, in solid solutions, the competition between the different spin anisotropies, as well as frustration, lead to a complex spin configuration. These measurements reveal that a 40% substitution of Er for Gd is sufficient for generating a phase diagram similar to the one for the ErB4 system, characterized by the occurrence of plateau phases and other exotic features attributed to the interplay of competing magnetic anisotropies.
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(This article belongs to the Special Issue Exclusive Collection: Papers from the Editorial Board Members of Magnetism)
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Open AccessArticle
Changes in Material Behavior according to the Amount of Recycled Magnetic Materials in Polymer-Bonded Magnets Based on Thermoplastics
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Uta Rösel and Dietmar Drummer
Magnetism 2024, 4(1), 1-23; https://doi.org/10.3390/magnetism4010001 - 15 Jan 2024
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The applications of polymer-bonded magnets are increasing within drive technology mostly because of new concepts concerning the magnetic excitation of direct current (DC) or synchronous machines. To satisfy this rising demand for hard magnetic filler particles—mainly rare earth materials—in polymer-bonded magnets, a recycling
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The applications of polymer-bonded magnets are increasing within drive technology mostly because of new concepts concerning the magnetic excitation of direct current (DC) or synchronous machines. To satisfy this rising demand for hard magnetic filler particles—mainly rare earth materials—in polymer-bonded magnets, a recycling strategy for thermoplastic-based bonded magnets has to be found that can be applied to polymer-bonded magnets. The most important factor for the recycling strategy is the filler material, especially when using rare earth materials, as those particles are associated with limited resources and high costs. However, thermoplastic-based bonded magnets reveal the opportunity to reuse the compound material system without separation of the filler from the matrix. Most known recycling strategies focus on sintered magnets, which leads to highly limited knowledge in terms of strategies for recycling bonded magnets. This paper illustrates the impact of different amounts of recycling material within the material system on material behavior and magnetic properties that can be achieved by taking different flow conditions and varying gating systems into account. The recycled material is generated by the mechanical reuse of shreds. We found that a supporting effect can be achieved with up to 50% recycled material in the material system, which leads to only minimal changes in the material’s behavior. Furthermore, changes in magnetic properties in terms of recycled material are affected by the gating system. To reduce the reduction in magnetic properties, the number of pin points should be as low as possible, and they should located in the middle. The filler orientation of the recycled material is minimally influenced by the outer magnetic field and, therefore, mainly follows the flow conditions. These flow conditions are likely to be affected by elastic flow proportions with increasing amounts of recycled material.
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Open AccessArticle
Estimation of Iron Loss in Permanent Magnet Synchronous Motors Based on Particle Swarm Optimization and a Recurrent Neural Network
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Kai Xu, Youguang Guo, Gang Lei and Jianguo Zhu
Magnetism 2023, 3(4), 327-342; https://doi.org/10.3390/magnetism3040025 - 11 Dec 2023
Cited by 2
Abstract
The popularity of permanent magnet synchronous motors (PMSMs) has increased in recent years due to their high efficiency, compact size, and low maintenance needs. Calculating iron loss in PMSMs is crucial for designing and optimizing PMSMs to achieve high efficiency and a long
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The popularity of permanent magnet synchronous motors (PMSMs) has increased in recent years due to their high efficiency, compact size, and low maintenance needs. Calculating iron loss in PMSMs is crucial for designing and optimizing PMSMs to achieve high efficiency and a long lifespan, as this can significantly affect motor performance. However, multiple factors influence the accuracy of iron loss calculations in PMSMs, including the intricate magnetic behavior of the motor under different operating conditions, as well as the influence of the motor’s dynamic behavior during the operation process. This paper proposes a method based on particle swarm optimization (PSO) and a recurrent neural network (RNN) to estimate the iron loss in PMSMs, independent of the empirical iron loss formula. This method establishes an iron loss calculation model considering high-order harmonics, rotating magnetization, and temperature factors. Accounting for the multifactor influence, the model studies the law of loss change under different magnetic flux densities, frequencies, and temperature conditions. To avoid the deviation problem caused by conventional polynomial fitting, a multilayer RNN and PSO are used to train and optimize the neural network. Iron loss in complex cases beyond the measurement range can be accurately estimated. The proposed method helps achieve a PMSM iron loss calculation model with broad applicability and high accuracy.
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(This article belongs to the Special Issue Digital Twins for Magnetic Devices)
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Open AccessArticle
Analytical Modelling of the Slot Opening Function
by
Antonino Di Gerlando and Claudio Ricca
Magnetism 2023, 3(4), 308-326; https://doi.org/10.3390/magnetism3040024 - 3 Nov 2023
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The slot opening function, also called relative air gap permeance, is a function which, multiplied by the flux density distribution of a slotless geometry, gives the flux density distribution of a slotted configuration. Here, the magnetic field inside the air gap of a
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The slot opening function, also called relative air gap permeance, is a function which, multiplied by the flux density distribution of a slotless geometry, gives the flux density distribution of a slotted configuration. Here, the magnetic field inside the air gap of a multi-slot surface facing a smooth one was studied, by solving the Laplace equation inside the air gap, in terms of a Fourier series. To obtain the Fourier coefficients, at first, the conformal mapping analytical solution of a single-slot configuration along the smooth surface, was considered. Then, the principle of superposition of the single-slot lost flux density distributions was applied to obtain the multi-slot distribution. The approach is valid in general, and in the case of interference among the flux density distributions of adjacent slots, where their mutual effect cannot be neglected. The field distributions obtained by using the proposed slot opening functions were compared with FEM simulations, showing satisfactory agreement. The numerical accuracy limits were also analysed and discussed.
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Open AccessFeature PaperArticle
Swirling of Horizontal Skyrmions into Hopfions in Bulk Cubic Helimagnets
by
Andrey O. Leonov
Magnetism 2023, 3(4), 297-307; https://doi.org/10.3390/magnetism3040023 - 19 Oct 2023
Cited by 1
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Magnetic hopfions are three-dimensional topological solitons embedded into a homogeneously magnetized background. The internal structure of hopfions is distinguished by the linked preimages—closed loops with a single orientation of the magnetization on the target space —and is thus characterized by the
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Magnetic hopfions are three-dimensional topological solitons embedded into a homogeneously magnetized background. The internal structure of hopfions is distinguished by the linked preimages—closed loops with a single orientation of the magnetization on the target space —and is thus characterized by the integer Hopf index . Alternatively, hopfions can be visualized as a result of the swirling of two-dimensional bimerons around the direction of an applied magnetic field. Since the bimeron consists of a circular core and an anti-skyrmion crescent, two hopfion varieties can be achieved with either bimeron constituent facing the hopfion interior. In bulk cubic helimagnets, however, the applied magnetic field leads to a spontaneous collapse of hopfions, i.e., the eigen-energy of hopfions has the minimum for zero hopfion radius R. Anti-hopfions with , in this case, pass through the intermediate toron state with two-point defects. Here, we demonstrate that the competing cubic and exchange anisotropies inherent in cubic non-centrosymmetric magnets (e.g., in the Mott insulator Cu OSeO ) as a third level of the hierarchy of energy scales following the exchange and Dzyaloshinskii–Moriya interactions, may shift the energy minimum into the region of finite hopfion radii.
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Open AccessArticle
A Novel Analytical Formulation of the Magnetic Field Generated by Halbach Permanent Magnet Arrays
by
Antonino Di Gerlando, Simone Negri and Claudio Ricca
Magnetism 2023, 3(4), 280-296; https://doi.org/10.3390/magnetism3040022 - 5 Oct 2023
Cited by 3
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This paper presents an analytical study of the air-gap magnetic field of a surface permanent magnet (SPM) linear, slot-less machine with a Halbach PM configuration, under the no-load condition. While other analytical formulations of the magnetic field generated by PMs are available, they
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This paper presents an analytical study of the air-gap magnetic field of a surface permanent magnet (SPM) linear, slot-less machine with a Halbach PM configuration, under the no-load condition. While other analytical formulations of the magnetic field generated by PMs are available, they exhibit some drawbacks, such as only providing a Fourier series, or being suitable to determine magnetic field average values, but not local magnetic field distributions. On the contrary, the proposed approach allows the determination of a unique, closed-form formulation for the slot-less machine air-gap field. This is obtained starting from the complex expression of the magnetic field of a conductor, inside the air gap, between two parallel smooth iron surfaces, obtained by means of the method of images. The magnetic field due to an infinitesimal conductor belonging to a current sheet is then integrated along a segment, providing the expression of the magnetic field due to the corresponding linear current density distribution, for current sheets perpendicular or parallel to the iron surfaces. Any Halbach PM segment disposition can, hence, be obtained via a suitable combination of field distributions generated by couples of current sheets with perpendicular and parallel orientation. Lastly, the no-load magnetic field expression with a Halbach array of PMs is retrieved. The proposed analytical model provides an accurate representation of the magnetic field distribution produced by any Halbach array, with an arbitrary number of segments and orientations. Additionally, the results obtained from the proposed analytical expressions are compared with FEM simulations realized by commercial software, and show an excellent agreement.
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Open AccessArticle
Zero-Pole Optimization of a Novel High-Quality-Factor Planar Helical Resonator
by
Reza Kamali-Sarvestani and John D. Williams
Magnetism 2023, 3(4), 267-279; https://doi.org/10.3390/magnetism3040021 - 28 Sep 2023
Abstract
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A novel micro-solenoid resonator has been designed, simulated, and measured. The solenoid core consisted of a DuroidTM circuit board with a relative permittivity of 2.2. The resonator design incorporated four embedded copper vias with a radius of 125 µm and three surface
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A novel micro-solenoid resonator has been designed, simulated, and measured. The solenoid core consisted of a DuroidTM circuit board with a relative permittivity of 2.2. The resonator design incorporated four embedded copper vias with a radius of 125 µm and three surface conductors to form a rectangular coil. A pitch size of 250 µm was used for a 3.02 mm thick substrate. To enhance the resonator’s performance at higher frequencies, a capacitance was introduced in series through the via. This additional capacitor effectively couples the inductance, resistance, and stray capacitance. The optimization of the quality factor was investigated through pole transfer analysis, resulting in an increased resonance frequency of 12.25 GHz and an elevated Q-factor of 306. Moreover, besides its very high Q-factor, this resonator offers a simplified design and easy integration. An analytical lumped circuit model was employed to investigate the design, and the measured S-parameters closely matched the analytical model and electromagnetic simulation results. The tuned resonator exhibited a superior quality factor compared to other micro-resonators.
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Open AccessArticle
Two-Step Magnetic Ordering in Intercalated Niobium Dichalcogenide MnXNbS2
by
Fedor Mushenok, Artem Shevchun, Dmitriy Shovkun and Maria Prokudina
Magnetism 2023, 3(3), 259-266; https://doi.org/10.3390/magnetism3030020 - 4 Sep 2023
Abstract
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Transition metal dichalcogenides are studied due to the possibility of creating nanoscale semiconductor devices, as well as fundamental issues of magnetic ordering. We researched the crystal structure and magnetic properties of niobium dichalcogenide Mn0.30NbS2. The results of the X-ray
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Transition metal dichalcogenides are studied due to the possibility of creating nanoscale semiconductor devices, as well as fundamental issues of magnetic ordering. We researched the crystal structure and magnetic properties of niobium dichalcogenide Mn0.30NbS2. The results of the X-ray study showed the possible existence of an intermediate 2 a0·2 a0 structure between the “basic” superstructures. Also, two local maximums were found in the temperature dependence of the dynamic magnetic susceptibility. These features can indirectly confirm the presence of a transition superstructure and reflect the two-step nature of the magnetic ordering.
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