Magnetism

14 pages, 4328 KB

Open AccessArticle

Analysis and Design of a Brushless WRSM with Harmonic Excitation Based on Electromagnetic Induction Power Transfer Optimization

by Arsalan Arif, Farhan Arif, Zuhair Abbas, Ghulam Jawad Sirewal, Muhammad Saleem, Qasim Ali and Mukhtar Ullah

Magnetism 2025, 5(4), 26; https://doi.org/10.3390/magnetism5040026 - 18 Oct 2025

Abstract

This paper proposes a method to analyze the effect of the rotor’s harmonic winding design and the output of a brushless wound rotor synchronous machine (WRSM) for optimal excitation power transfer. In particular, the machine analyzed by the finite-element method was a 48-slot [...] Read more.

This paper proposes a method to analyze the effect of the rotor’s harmonic winding design and the output of a brushless wound rotor synchronous machine (WRSM) for optimal excitation power transfer. In particular, the machine analyzed by the finite-element method was a 48-slot eight-pole 2D model. The subharmonic magnetomotive force was additionally created in the air gap flux, which induces voltage in the harmonic winding of the rotor. This voltage is rectified and fed to the field winding through a full bridge rectifier. Eventually, a direct current (DC) flows to the field winding, removing the need for external excitation through brushes and sliprings. The effect of the number of harmonic winding turns is analyzed and the field winding turns were varied with respect to the available rotor slot space. Optimization of the harmonic excitation part of the machine will maximize the rotor excitation for regulation purposes and optimize the torque production at the same time. Two-dimensional finite-element analysis has been performed in ANSYS Maxwell 19 to obtain the basic results for the design of the machine. Full article

(This article belongs to the Special Issue Rare-Earth-Free Permanent Magnet Motors and Generators for Use in Electric Vehicles and Wind Turbines)

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10 pages, 2359 KB

Open AccessArticle

Magnetic Field Suppression of the Martensitic Transformation in Mn-Based MnNi(Fe)Sn Metamagnetic Shape Memory Heusler Alloys

by Patricia Lázpita, Natalia Ahiova Río-López, David Mérida, Emily (Leonie Quinlyn Nowalaja) Ammerlaan, Uli Zeitler, Volodymyr Chernenko and Jon Gutiérrez

Magnetism 2025, 5(4), 25; https://doi.org/10.3390/magnetism5040025 - 16 Oct 2025

Abstract

Heusler-type metamagnetic shape memory alloys (MMSMAs) exhibit a large functional response associated with a first-order martensitic transformation (MT). The strong magneto-structural coupling combined with the presence of mixed magnetic interactions enables controlling this MT by means of a magnetic field, resulting in different [...] Read more.

Heusler-type metamagnetic shape memory alloys (MMSMAs) exhibit a large functional response associated with a first-order martensitic transformation (MT). The strong magneto-structural coupling combined with the presence of mixed magnetic interactions enables controlling this MT by means of a magnetic field, resulting in different multifunctional properties, among them giant magnetoresistance, metamagnetic shape memory effect (MMSM), or inverse magnetocaloric effect (MCE). Not only the shift rate of MT as a function of the magnetic field but also its eventual suppression are key parameters in order to develop these effects. Here we present our findings concerning a detailed study of the magnetic field-induced MT and its suppression in MnNi(Fe)Sn MMSMAs, by applying strong steady magnetic fields up to 33 T. These measurements will lead to the creation of the T-μ₀H phase diagrams of the MT. Moreover, we will also give light to the effect of Fe—content and, as a direct consequence, the magnetic coupling on the suppression of the magnetostructural transformation. Full article

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18 pages, 698 KB

Open AccessArticle

Locally Odd-Parity Hybridization Induced by Spiral Magnetic Textures

by Satoru Hayami

Magnetism 2025, 5(4), 24; https://doi.org/10.3390/magnetism5040024 - 2 Oct 2025

Abstract

We study unconventional multipole moments arising from noncollinear magnetic structures within an augmented framework encompassing electric, magnetic, magnetic toroidal, and electric toroidal multipoles. Employing a tight-binding model for an s-p hybridized orbital system, we analyze two spiral magnetic textures and classify [...] Read more.

We study unconventional multipole moments arising from noncollinear magnetic structures within an augmented framework encompassing electric, magnetic, magnetic toroidal, and electric toroidal multipoles. Employing a tight-binding model for an s-p hybridized orbital system, we analyze two spiral magnetic textures and classify the resulting multipoles according to magnetic point group symmetry. Different spiral wave types, such as cycloidal and proper-screw forms, activate distinct multipole components, with odd-parity multipoles emerging from local s-p parity mixing induced by magnetically driven inversion-symmetry breaking. Calculated multipole structure factors reveal finite-q peaks originating from higher-order magnetic-dipole-scattering processes and their characteristic couplings between Fourier components of the magnetic dipole texture. Our results demonstrate that magnetic ordering can generate parity-mixed states without intrinsic structural inversion asymmetry, offering new pathways to realize cross-correlation phenomena in functional magnetic materials. Full article

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15 pages, 2516 KB

Open AccessArticle

Enhancement of Heat Transfer Accompanied by a Decrease in Kinetic Energy Due to Magnetic Field Imposition in Liquid Metal Natural Convection

by Shu Kondo, Takuya Masuda, Masaki Sakaguchi, Yasutaka Hayamizu, M. M. A. Alam and Toshio Tagawa

Magnetism 2025, 5(3), 23; https://doi.org/10.3390/magnetism5030023 - 22 Sep 2025

Abstract

Natural convection of liquid metals under magnetic fields is a phenomenon of interest in various industrial and scientific applications, including fusion reactor blankets and magnetohydrodynamic (MHD) power systems. While the application of a magnetic field generally suppresses convection and reduces the heat transfer [...] Read more.

Natural convection of liquid metals under magnetic fields is a phenomenon of interest in various industrial and scientific applications, including fusion reactor blankets and magnetohydrodynamic (MHD) power systems. While the application of a magnetic field generally suppresses convection and reduces the heat transfer rate, recent studies have reported cases where the Nusselt number increases under certain magnetic field conditions. In this study, we conduct numerical simulations of natural convection in an annular container filled with a liquid metal, subject to a circumferential static magnetic field. The governing equations, incorporating both temperature and electromagnetic fields, are solved using a high-order finite difference scheme. The results show that, within a specific range of parameters, the Nusselt number increases at moderate Hartmann numbers, even under low Rayleigh number conditions. Notably, this enhancement in heat transfer occurs alongside a reduction in kinetic energy, indicating that convective strength is not necessarily the dominant factor. Further analysis confirms that this phenomenon weakens and eventually vanishes as the Rayleigh number approaches 10⁶. These findings provide evidence that magnetic field-induced heat transfer enhancement can occur without a corresponding increase in convective motion, thereby challenging conventional assumptions in magnetoconvection theory. Full article

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18 pages, 3329 KB

Open AccessArticle

Landau Levels and Electronic States for Pseudospin-1 Lattices with a Bandgap: Application to a Lieb Lattice

by Liubov Zhemchuzhna, Lovely Joseph, Andrii Iurov, Godfrey Gumbs and Danhong Huang

Magnetism 2025, 5(3), 22; https://doi.org/10.3390/magnetism5030022 - 16 Sep 2025

Abstract

We have carried out detailed theoretical and numerical calculations and developed a physics-based model for quantitatively describing the Landau levels of several pseudospin-1 structures with a flat band and a finite bandgap in their electronic-energy spectrum under a strong and uniform magnetic field. [...] Read more.

We have carried out detailed theoretical and numerical calculations and developed a physics-based model for quantitatively describing the Landau levels of several pseudospin-1 structures with a flat band and a finite bandgap in their electronic-energy spectrum under a strong and uniform magnetic field. We have investigated the Landau-level-based dynamics, as well as the corresponding eigenstates, for gapped graphene, a dice lattice with both a zero and finite bandgap and, eventually, for the Lieb lattice, which represents a separate type of square lattice with a very special non-symmetric (elevated) location of the flat band which intersects the conduction band at its lowest point. Exact analytical consideration of Landau-level states has been performed and explained when dealing with all types of considered lattices. Our model could be further generalized for treating cases with an arbitrary position for the flat band between the valence and conduction bands. Our current results have direct implications for a deep-level investigation of the quantum Hall effect, as well as other magnetic and topological properties of these novel materials. Full article

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12 pages, 20763 KB

Open AccessArticle

Comparison of Two- and Three-Phase Devices Generating a Rotating Magnetic Fieldfor Magnetic Hyperthermia Applications

by Andrzej Skumiel

Magnetism 2025, 5(3), 21; https://doi.org/10.3390/magnetism5030021 - 10 Sep 2025

Abstract

This article describes systems generating high-frequency rotating magnetic fields for magnetic hyperthermia treatments. It covers two- and three-phase device systems powered by rectangular signals. A passive bandpass filter tuned to a specific frequency (100 kHz) is placed between the magnetic circuits and the [...] Read more.

This article describes systems generating high-frequency rotating magnetic fields for magnetic hyperthermia treatments. It covers two- and three-phase device systems powered by rectangular signals. A passive bandpass filter tuned to a specific frequency (100 kHz) is placed between the magnetic circuits and the DC power source powering the device. The paper compares the electrical parameters of both solutions, including the supply voltage, magnetic field strength amplitude H, and magnetizing current I_L as a function of the supply voltage (U_dc). At a fixed supply voltage U_dc, the magnetizing current I_L and the rotating magnetic field strength amplitude H are approximately twice as large for the three-phase system as for the two-phase system. The relationships between the magnetizing currents I_L and the magnetic field strength amplitude H as a function of the supply voltage U_dc are linear. Full article

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19 pages, 2476 KB

Open AccessArticle

Magnetic Field Analysis of Unconventional High Surge Impedance Loading (HSIL) Transmission Lines with Different Subconductor Configurations: Numerical Comparisons and Performance Evaluation

by Easir Arafat, Babak Porkar and Mona Ghassemi

Magnetism 2025, 5(3), 20; https://doi.org/10.3390/magnetism5030020 - 5 Sep 2025

Abstract

High-voltage transmission lines are the backbone of modern power systems, facilitating the delivery of electricity from diverse generation sources, including conventional power plants and renewable energy systems, to consumers. As the electricity demand grows, the expansion of transmission infrastructure becomes essential to connecting [...] Read more.

High-voltage transmission lines are the backbone of modern power systems, facilitating the delivery of electricity from diverse generation sources, including conventional power plants and renewable energy systems, to consumers. As the electricity demand grows, the expansion of transmission infrastructure becomes essential to connecting new consumers with power suppliers. However, traditional transmission lines require significant right-of-way, posing challenges related to land use and environmental impact, as well as limited loadability. To address this issue, compact unconventional High Surge Impedance Loading (HSIL) transmission lines offer a viable solution by reducing right-of-way requirements while enhancing line natural power, mainly leading to less voltage drop. Before the implementation of the new unconventional HSIL lines, it is crucial to assess key parameters, such as magnetic field distribution under the lines, to ensure compliance with environmental and safety standards. This paper presents a numerical analysis of the magnetic field characteristics of compact unconventional HSIL transmission lines with different subconductor configurations. The results show that the proposed HSIL designs can reduce the magnetic field at ground level by up to 71.74% compared to a conventional 500 kV line near the center, as well as by up to 74% at the right-of-way edge, while maintaining magnetic field levels well below the limits set by ICNIRP and state-specific regulations. This study evaluates the magnetic field distribution within the right-of-way, providing insights into the electromagnetic performance and potential implications for transmission line design. Full article

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14 pages, 20914 KB

Open AccessArticle

Effect of the Non-Magnetic Ion Doping on the Magnetic Behavior of MgCr₂O₄

by Fuxi Zhou, Zheng He, Donger Cheng, Han Ge, Wenjing Zhang, Xiao Wang, Pengfei Zhou, Wanju Luo, Zhengdong Fu, Xinzhi Liu, Liusuo Wu, Lunhua He, Yanchun Zhao and Erxi Feng

Magnetism 2025, 5(3), 19; https://doi.org/10.3390/magnetism5030019 - 25 Aug 2025

Abstract

Geometrically frustrated magnets exhibit exotic excitations due to competing interactions between spins. The spinel compound MgCr₂O₄, a three-dimensional Heisenberg antiferromagnet, hosts both spin-wave and spin-resonance modes, but the origin of its resonant excitations remains debated. Suppressing magnetic order via [...] Read more.

Geometrically frustrated magnets exhibit exotic excitations due to competing interactions between spins. The spinel compound MgCr₂O₄, a three-dimensional Heisenberg antiferromagnet, hosts both spin-wave and spin-resonance modes, but the origin of its resonant excitations remains debated. Suppressing magnetic order via non-magnetic doping can help isolate these modes in neutron scattering studies. We synthesized Ga³⁺ and Cd²⁺-doped MgCr₂O₄ via solid-state reaction and analyzed their structure and magnetism. Ga³⁺ doping (0–20%) causes anomalous lattice shrinkage due to site disorder from Ga³⁺ occupying both Mg²⁺ and Cr³⁺ sites. Magnetically, Ga³⁺ doping drives the system from the antiferromagnetic order to a spin-glass state, fully suppressing magnetic ordering at 20% doping. In contrast, Cd²⁺ replaces only Mg²⁺, expanding the lattice and meantime inducing strong spin-glass behavior. At 10% Cd²⁺, long-range antiferromagnetic order is entirely suppressed. Thus, 10% Cd-doped MgCr₂O₄ offers an ideal platform to study the resonant magnetic excitations without any spin-wave interference. Full article

(This article belongs to the Special Issue Research on the Magnetism of Heavy-Fermion Systems)

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22 pages, 6376 KB

Open AccessArticle

Components for an Inexpensive CW-ODMR NV-Based Magnetometer

by André Bülau, Daniela Walter and Karl-Peter Fritz

Magnetism 2025, 5(3), 18; https://doi.org/10.3390/magnetism5030018 - 1 Aug 2025

Abstract

Quantum sensing based on NV-centers in diamonds has been demonstrated many times in multiple publications. The majority of publications use lasers in free space or lasers with fiber optics, expensive optical components such as dichroic mirrors, or beam splitters with dichroic filters and [...] Read more.

Quantum sensing based on NV-centers in diamonds has been demonstrated many times in multiple publications. The majority of publications use lasers in free space or lasers with fiber optics, expensive optical components such as dichroic mirrors, or beam splitters with dichroic filters and expensive detectors, such as Avalanche photodiodes or single photon detectors, overall, leading to custom and expensive setups. In order to provide an inexpensive NV-based magnetometer setup for educational use in schools, to teach the three topics, fluorescence, optically detected magnetic resonance, and Zeeman splitting, inexpensive, miniaturized, off-the-shelf components with high reliability have to be used. The cheaper such a setup, the more setups a school can afford. Hence, in this work, we investigated LEDs as light sources, considered different diamonds for our setup, tested different color filters, proposed an inexpensive microwave resonator, and used a cheap photodiode with an appropriate transimpedance amplifier as the basis for our quantum magnetometer. As a result, we identified cheap and functional components and present a setup and show that it can demonstrate the three topics mentioned at a hardware cost <EUR 100. Full article

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26 pages, 38696 KB

Open AccessReview

Altermagnetism and Altermagnets: A Brief Review

by Rupam Tamang, Shivraj Gurung, Dibya Prakash Rai, Samy Brahimi and Samir Lounis

Magnetism 2025, 5(3), 17; https://doi.org/10.3390/magnetism5030017 - 23 Jul 2025

Cited by 3

Abstract

Recently, a new class of magnetic material, termed altermagnets, has caught the attention of the magnetism and spintronics community. The magnetic phenomenon arising from these materials differs from traditional ferromagnetism and antiferromagnetism. It generally lacks net magnetization and is characterized by unusual non-relativistic [...] Read more.

Recently, a new class of magnetic material, termed altermagnets, has caught the attention of the magnetism and spintronics community. The magnetic phenomenon arising from these materials differs from traditional ferromagnetism and antiferromagnetism. It generally lacks net magnetization and is characterized by unusual non-relativistic spin-splitting and broken time-reversal symmetry. This leads to novel transport properties, such as the anomalous Hall effect, the crystal Nernst effect, and spin-dependent phenomena. Spin-dependent phenomena such as spin currents, spin-splitter torques, and high-frequency dynamics emerge as key characteristics in altermagnets. This paper reviews the main aspects pertaining to altermagnets by providing an overview of theoretical investigations and experimental realizations. We discuss the most recent developments in altermagnetism and prospects for exploiting its unique properties in next-generation devices. Full article

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23 pages, 816 KB

Open AccessArticle

Large Angular Momentum

by Kenichi Konishi and Roberto Menta

Magnetism 2025, 5(3), 16; https://doi.org/10.3390/magnetism5030016 - 9 Jul 2025

Abstract

The quantum states of a spin

\frac{1}{2}

(a qubit) are parametrized by the space

{CP}^{1} \sim S^{2}

, the Bloch sphere. A spin j for a generic j (a

2 j + 1

-state system) is represented instead by a [...] Read more.

The quantum states of a spin

\frac{1}{2}

(a qubit) are parametrized by the space

{CP}^{1} \sim S^{2}

, the Bloch sphere. A spin j for a generic j (a

2 j + 1

-state system) is represented instead by a point in a larger space,

{CP}^{2 j}

. Here we study the state of a single angular momentum/spin in the limit

j \to \infty

. A special class of states,

| j, n ⟩ \in {CP}^{2 j}

, with spin oriented towards definite spatial directions,

n \in S^{2}

, i.e.,

(\hat{J} \cdot n) | j, n ⟩ = j | j, n ⟩

, are found to behave as classical angular momenta,

j n

, in this limit. Vice versa, general spin states in

{CP}^{2 j}

do not become classical, even at a large j. We study these questions by analyzing the Stern–Gerlach processes, the angular momentum composition rule, and the rotation matrix. Our observations help to better clarify how classical mechanics emerges from quantum mechanics in this context (e.g., with the unique trajectories of a particle carrying a large spin in an inhomogeneous magnetic field) and to make the widespread idea that large spins somehow become classical more precise. Full article

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15 pages, 689 KB

Open AccessArticle

Magnetic Toroidal Monopole in a Single-Site System

by Satoru Hayami

Magnetism 2025, 5(3), 15; https://doi.org/10.3390/magnetism5030015 - 25 Jun 2025

Abstract

A magnetic toroidal monopole, which characterizes time-reversal-odd polar-charge quantity, manifests itself not only in antiferromagnetism but also in time-reversal switching physical responses. We theoretically investigate an atomic-scale description of the magnetic toroidal monopole based on multipole representation theory, which consists of four types [...] Read more.

A magnetic toroidal monopole, which characterizes time-reversal-odd polar-charge quantity, manifests itself not only in antiferromagnetism but also in time-reversal switching physical responses. We theoretically investigate an atomic-scale description of the magnetic toroidal monopole based on multipole representation theory, which consists of four types of multipoles. We show that the magnetic toroidal monopole degree of freedom is activated as the off-diagonal imaginary hybridization between the single-site orbitals with the same orbital angular momentum but different principal quantum numbers. We demonstrate that the expectation value of the magnetic toroidal monopole becomes nonzero when both electric and magnetic fields are applied to the system. Full article

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17 pages, 3401 KB

Open AccessArticle

Ab Initio Investigation on the Magnetic Moments, Magnetocrystalline Anisotropy and Curie Temperature of Fe₂P-Based Magnets

by Stephan Erdmann, Halil İbrahim Sözen and Thorsten Klüner

Magnetism 2025, 5(2), 14; https://doi.org/10.3390/magnetism5020014 - 10 Jun 2025

Abstract

Permanent magnetic materials are essential for technological applications, with the majority of available magnets being either ferrites or materials composed of critical rare-earth elements, such as well-known Nd₂Fe₁₄B. The binary Fe₂P material emerges as a promising candidate [...] Read more.

Permanent magnetic materials are essential for technological applications, with the majority of available magnets being either ferrites or materials composed of critical rare-earth elements, such as well-known Nd₂Fe₁₄B. The binary Fe₂P material emerges as a promising candidate to address the performance gap, despite its relatively low Curie temperature

T_{C}

of 214 K. In this study, density functional theory was employed to investigate the effect of Si and Co substitution on the magnetic moments, magnetocrystalline anisotropy energy (MAE) and Curie temperature in

{Fe}_{2 - y}

Co_yP_1−xSi_x compounds. Our findings indicate that Si substitution enhances magnetic moments due to the increase in 3f-3f and 3f-3g interaction energies, which also contribute to higher

T_{C}

values. Conversely, Co substitution leads to a reduction in magnetic moments, attributable to the inherently lower magnetic moments of Co. In all examined cases of different Si concentrations, such as hexagonally structured

{Fe}_{2 - y}

Co_yP,

{Fe}_{2 - y}

Co_yP_0.92Si_0.08 and

{Fe}_{2 - y}

Co_yP_0.84Si_0.16, Co substitution increases the Curie temperatures by augmenting 3g-3g exchange interaction energies. Both Si and Co substitutions decrease the magnetocrystalline anisotropy energy, resulting in the loss of the easy magnetization direction at higher Co contents. However, higher Si concentrations appear to confer resilience against the loss. In summary, Si and Co substitutions effectively modify the investigated magnetic properties. Nonetheless, to preserve a high MAE, the extent of substitution should be optimized. Full article

(This article belongs to the Special Issue Rare-Earth-Free Permanent Magnet Motors and Generators for Use in Electric Vehicles and Wind Turbines)

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17 pages, 3610 KB

Open AccessArticle

Semi-Active Vibration Control for High-Speed Elevator Using Magnetorheological Damper

by Marcos Gonçalves, Maria E. K. Fuziki, Jose M. Balthazar, Giane G. Lenzi and Angelo M. Tusset

Magnetism 2025, 5(2), 13; https://doi.org/10.3390/magnetism5020013 - 8 Jun 2025

Abstract

This paper presents the results of investigating the application of magnetorheological fluids in controlling the lateral and angular vibrations of a high-speed elevator. Numerical simulations are performed for a mathematical model with two degrees of freedom. The lateral and rotational accelerations are analyzed [...] Read more.

This paper presents the results of investigating the application of magnetorheological fluids in controlling the lateral and angular vibrations of a high-speed elevator. Numerical simulations are performed for a mathematical model with two degrees of freedom. The lateral and rotational accelerations are analyzed for different travel speeds to determine passenger comfort levels. To attenuate the elevator vibrations, the introduction of a magnetorheological damper in parallel with the passive damper of the elevator rollers is considered. To semi-actively control the dissipative forces of the magnetorheological fluids, a State-Dependent Riccati Equation (SDRE control) is proposed. The numerical results demonstrate that using an MR damper makes it possible to reduce the acceleration levels of the elevator cabin, thus improving passenger comfort and reducing the elevator’s vibration levels and wear on the mechanical and electronic components of the elevator. In addition to the results, a detailed sensitivity analysis is presented. Full article

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14 pages, 2243 KB

Open AccessArticle

Effect of High-Harmonic Wave-Vector Interactions on the Single-Q Spiral State

by Satoru Hayami

Magnetism 2025, 5(2), 12; https://doi.org/10.3390/magnetism5020012 - 28 May 2025

Abstract

We investigate the role of high-harmonic wave-vector interactions, which affect the stability of the single-Q spiral state and often result in the formation of multiple-Q states. By performing simulated annealing for an effective spin model on a two-dimensional square lattice, we [...] Read more.

We investigate the role of high-harmonic wave-vector interactions, which affect the stability of the single-Q spiral state and often result in the formation of multiple-Q states. By performing simulated annealing for an effective spin model on a two-dimensional square lattice, we examine the modulation of the single-Q spiral spin configuration by the high-harmonic wave-vector interaction. As a result, we find that the interactions at particular high-harmonic wave vectors affect the stability of the single-Q spiral state. In particular, the incorporation of interactions at high-harmonic wave vectors formed by the sum of two mutually perpendicular ordering wave vectors can lead to the emergence of three double-Q states and a square skyrmion crystal. The present study unveils the importance of high-harmonic wave-vector interactions in order to realize complicated noncoplanar spin textures. Full article

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12 pages, 498 KB

Open AccessArticle

Influence of Magnetic Field on Atrazine Adsorption and Degradation by Ferroxite and Hematite

by Marcos Antônio Sousa, Mateus Aquino Gonçalves, Thais Aparecida Sales, Jessica Boreli dos Reis Lino, Stéfany Gonçalves de Moura, Joaquim Paulo da Silva and Teodorico Castro Ramalho

Magnetism 2025, 5(2), 11; https://doi.org/10.3390/magnetism5020011 - 21 May 2025

Abstract

This study approaches the characterization of Ferroxite and Hematite and the test of their magnetic properties on the degradation and adsorption of Atrazine, an herbicide of the triazine class. This herbicide was compared with a sample of Ferroxite in the absence of a [...] Read more.

This study approaches the characterization of Ferroxite and Hematite and the test of their magnetic properties on the degradation and adsorption of Atrazine, an herbicide of the triazine class. This herbicide was compared with a sample of Ferroxite in the absence of a magnetic field and with Hematite, a non-magnetic material which should not be attracted by the magnet. In the sample, the Atrazine determination was carried out by Fenton analysis. Preliminary results were satisfactory, gathering a reduction rate up to 85% for Ferroxite in the presence of a magnetic field and 53% for Hematite. The Fenton reaction, however, showed an 87% reduction rate for Ferroxite in the presence of a magnetic field, and 56% for Hematite. These findings have shown that there is a relation between the magnetic field intensity and the adsorption capacity for these materials. Full article

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13 pages, 9500 KB

Open AccessArticle

Resilience of LTE-A/5G-NR Links Against Transient Electromagnetic Interference

by Sharzeel Saleem and Mir Lodro

Magnetism 2025, 5(2), 10; https://doi.org/10.3390/magnetism5020010 - 22 Apr 2025

Abstract

This paper presents a comparative analysis of a long-term evolution advanced (LTE-A) and fifth-generation new radio (5G-NR), focusing on the effects of transient electromagnetic interference (EMI) caused by catenary–pantograph contact in a railway environment.A software-defined radio (SDR)-based prototype was developed to evaluate the [...] Read more.

This paper presents a comparative analysis of a long-term evolution advanced (LTE-A) and fifth-generation new radio (5G-NR), focusing on the effects of transient electromagnetic interference (EMI) caused by catenary–pantograph contact in a railway environment.A software-defined radio (SDR)-based prototype was developed to evaluate the performance of LTE-A and 5G-NR links under the influence of transient interference. The results show that both links experience considerable degradation due to interference at different centre frequencies. Performance degradation is proportional to the gain of interference. The measurement results show that both links experience considerable performance degradation in the presence of transient EMI. Full article

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29 pages, 719 KB

Open AccessFeature PaperArticle

State Transitions and Hysteresis in a Transverse Magnetic Island Chain

by Gary M. Wysin

Magnetism 2025, 5(1), 9; https://doi.org/10.3390/magnetism5010009 - 12 Mar 2025

Abstract

A chain of dipole-coupled elongated magnetic islands whose long axes are oriented perpendicular to the chain is studied for its magnetization properties. With a magnetic field applied perpendicular to the chain, the competition between dipolar energy, shape anisotropy, and field energy leads to [...] Read more.

A chain of dipole-coupled elongated magnetic islands whose long axes are oriented perpendicular to the chain is studied for its magnetization properties. With a magnetic field applied perpendicular to the chain, the competition between dipolar energy, shape anisotropy, and field energy leads to three types of uniform states with distinct magnetizations: (1) oblique to the chain, (2) perpendicular to the chain, and (3) zero due to having alternating dipoles. The response of these states to a slowly varying field is analyzed, focusing on their stability limits and related oscillation modes, and the dependencies on the dipolar and anisotropy constants. Based on identifiable transitions among the three states and their instability points, the theoretically predicted zero-temperature magnetization curves show significant dependence on the anisotropy. The model suggests a path for designing advanced materials with desired magnetic properties. Different geometries and magnetic media for the islands are considered. Full article

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18 pages, 5243 KB

Open AccessArticle

Simultaneous Spin and Point-Group Adaptation in Exact Diagonalization of Spin Clusters

by Shadan Ghassemi Tabrizi and Thomas D. Kühne

Magnetism 2025, 5(1), 8; https://doi.org/10.3390/magnetism5010008 - 12 Mar 2025

Cited by 1

Abstract

While either a spin or point-group adaptation is straightforward when considered independently, the standard technique for factoring isotropic spin Hamiltonians by the total spin S and the irreducible representation

Γ

of the point group is limited by the complexity of the transformations between [...] Read more.

While either a spin or point-group adaptation is straightforward when considered independently, the standard technique for factoring isotropic spin Hamiltonians by the total spin S and the irreducible representation

Γ

of the point group is limited by the complexity of the transformations between different coupling schemes that are related in terms of their site permutations. To overcome these challenges, we apply projection operators directly to uncoupled basis states, enabling the simultaneous treatment of spin and point-group symmetry without the need for recoupling transformations. This provides a simple and efficient approach for the exact diagonalization of isotropic spin models, which we illustrate, with applications in Heisenberg spin rings and polyhedra, including systems that are computationally inaccessible with conventional coupling techniques. Full article

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