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Magnetism, Volume 4, Issue 1 (March 2024) – 6 articles

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18 pages, 7116 KiB  
Article
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 | Viewed by 1343
Abstract
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 [...] Read more.
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. Full article
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19 pages, 2835 KiB  
Article
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
Viewed by 1197
Abstract
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 [...] Read more.
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. Full article
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7 pages, 4310 KiB  
Communication
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
Viewed by 1041
Abstract
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 [...] Read more.
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. Full article
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12 pages, 1655 KiB  
Article
Coexistence of Long-Range Magnetic Order and Magnetic Frustration of a Novel Two-Dimensional S = 1/2 Structure: Na2Cu3(SeO3)4
by 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
Viewed by 1473
Abstract
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 [...] Read more.
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. Full article
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11 pages, 6358 KiB  
Article
Phase Diagram Mapping out the Complex Magnetic Structure of Single Crystals of (Gd, Er)B4 Solid Solutions
by 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
Viewed by 1493
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 [...] Read more.
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. Full article
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23 pages, 4868 KiB  
Article
Changes in Material Behavior according to the Amount of Recycled Magnetic Materials in Polymer-Bonded Magnets Based on Thermoplastics
by Uta Rösel and Dietmar Drummer
Magnetism 2024, 4(1), 1-23; https://doi.org/10.3390/magnetism4010001 - 15 Jan 2024
Viewed by 1135
Abstract
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 [...] Read more.
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. Full article
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