Rare-earth Magnets Research Articles

Superconductivity of rare-earth borides Dy1–xErxRh3.8Ru0.2B4 (x = 0, 0.2, 0.4) and Dy0.6Y0.4Rh3.85Ru0.15B4

The effect on the superconductivity of the partial replacement of one magnetic rare-earth element (Dy) by another (Er) in rhodium borides Dy1–xErxRh3.8Ru0.2B4 with x = 0, 0.2, 0.4 is studied. It was found that in Dy1–xErxRh3.8Ru0.2B4, with increasing Er content, the temperature of the superconducting transition increases significantly: from 3.7 K for x = 0 to 6 K for x = 0.4. It was demonstrated that the replacement of magnetic Er3+ with nonmagnetic Y3+ in the isostructural compounds Dy0.6Er0.4Rh3.8Ru0.2B4 (Tc ≈ 6 K) and Dy0.6Y0.4Rh3.85Ru0.15B4 (Tc ≈ 7 K) does not lead to a significant change in the temperature of the superconducting transition. The suppression of the superconducting state by the magnetism of rare-earth elements is not observed down to 1.5 K the lowest available temperature in the experiment.

Magnetic characterization of Sm(Fe1-x, Cox)11Ti (x = 0, 0.1) determined by heat-capacity measurement from very low to high temperatures

The thermodynamic and magnetic properties of SmFe11Ti and Sm(Fe0.9Co0.1)11Ti, which are candidates for the main constituents of rare-earth magnets, were investigated by measuring their heat capacities in the range of 2–1050 K. The Curie temperatures, TC, of SmFe11Ti and Sm(Fe0.9Co0.1)11Ti were found to be 582.9 and 705.0 K, respectively. Their magnetic moments, β, obtained from the magnetic entropies by separating the spin and lattice vibration terms were 20.09 and 22.71 (μB (compd)-1), respectively, which are consistent with the results of direct magnetization measurements. This indicates that the 3d magnetic moment of Fe, which provides the magnetization, becomes aligned by the effective exchange interaction between Sm 4f via Sm 5d and Fe 3d in a second-order phase transition. In Sm(Fe0.9Co0.1)11Ti, Co 3d strongly exchange-couples with Fe 3d, following the Slater-Pauling curves, and TC and β simultaneously increase. The Sommerfeld parameters of SmFe11Ti and Sm(Fe0.9Co0.1)11Ti indicate the inherent valence fluctuation of Sm; that is, the Sm 4f empty density of states was found to be occupied by the electrons surrounding the Sm atom, indicating low phase stability. These findings are expected to contribute to the design of materials with intrinsic magnetic properties.

Significant Progress for Hot-Deformed Nd-Fe-B Magnets: A Review.

High-performance Nd-Fe-B-based rare-earth permanent magnets play a crucial role in the application of traction motors equipped in new energy automobiles. In particular, the anisotropic hot-deformed (HD) Nd-Fe-B magnets prepared by the hot-press and hot-deformation process show great potential in achieving high coercivity due to their fine grain sizes of 200-400 nm, which are smaller by more than an order of magnitude compared to the traditional sintered Nd-Fe-B magnets. However, the current available coercivity of HD magnets is not as high as expected according to an empirical correlation between coercivity and grain size, only occupying about 25% of its full potential of the anisotropy field of the Nd2Fe14B phase. For the sake of achieving high-coercivity HD magnets, two major routes have been developed, namely the grain boundary diffusion process (GBDP) and the dual alloy diffusion process (DADP). In this review, the fundamentals and development of the HD Nd-Fe-B magnets are comprehensively summarized and discussed based on worldwide scientific research. The advances in the GBDP and DADP are investigated and summarized based on the latest progress and results. Additionally, the mechanisms of coercivity enhancement are discussed based on the numerous results of micromagnetic simulations to understand the structure-property relationships of the HD Nd-Fe-B magnets. Lastly, the magnetization reversal behaviors, based on the observation of magneto-optic Kerr effect microscopy, are analyzed to pinpoint the weak regions in the microstructure of the HD Nd-Fe-B magnets.

Two-dimensional 4f magnetic EuSn2X2 (X = P, As) monolayers: A first-principles study

Two-dimensional (2D) ferromagnetic semiconductors (FMSs) hold exciting and promising potential for application in spintronic devices at the nanoscale. Currently, most 2D FMSs are based on 3d electrons; 4f electrons can provide nontrivial magnetism but have been much less studied to date. This paper presents a theoretical study, via first-principles calculations, of EuSn2X2 (X = P, As) monolayers based on rare-earth cations with f-electrons. The results show that EuSn2X2 monolayers possess a large magnetization (7 μB/Eu), a controllable magnetic anisotropy energy, and a unique d-electron-mediated f–f exchange mechanism. Both types of EuSn2X2 (X = P, As) monolayers are FMSs with indirect bandgaps of 1.00 and 0.99 eV, respectively, based on the Heyd–Scuseria–Ernzerhof (HSE06) method, which can be transform to direct bandgap semiconductors under biaxial strain. Interestingly, under the latter, spin–orbit coupling interaction gradually replaces the dipole–dipole interaction in the dominant position of magnetic anisotropy, resulting in the magnetic easy axis changing from in-plane to the more desirable out-of-plane. Considering their excellent dynamic, thermal, and mechanical stabilities and small cleavage energy, these EuSn2X2 monolayers can be exfoliated from their synthesized bulk. Our study not only helps to understand the properties of 2D 4f rare-earth magnets but also signposts a route toward improving the performance of EuSn2X2 monolayers in nano-electronic devices.

Hybrid Quadrupole Lens for the Focusing Channel of the DARIA Complex

The results of synthesis and electromagnetic calculation of a hybrid quadrupole lens for a proton linear accelerator of a compact neutron source DARIA are presented. The lens includes a permanent magnet quadrupole with a fixed magnetic field gradient and an auxiliary electromagnetic quadrupole excited by a pulsed current. The permanent magnet quadrupole is made of radiation-resistant rare-earth magnet, and the electromagnetic quadrupole is designed to compensate for permanent magnet magnetization losses resulting from radiation degradation as neutron fluence accumulates during accelerator operation. A hybrid quadrupole lens can be applied for fast adjustment of the focusing channel when accelerating ion beams with different ion mass-to-charge ratios.

Triggering Magnets for Wiegand Sensors: Electrodeposited and Origami-Magnetized CoNiP Micro-Magnets.

Miniature sensors are key components for applications in the Internet of Things (IoT), wireless sensor networks, autonomous vehicles, smart cities, and smart manufacturing. As a miniature and self-powered magnetic sensor, the Wiegand sensor possesses advantageous traits including changing-rate-independent output, low cost, and remarkable repeatability and reliability. A typical Wiegand sensor requires hard magnetic pole pieces that provide external fields for triggering voltage outputs that are called Wiegand pulses. However, the wire-shaped sensing element of Wiegand sensors is the critical issue that limits the design, selection, and adoption of the external triggering magnets. Currently, the widely used pole piece materials are rare-earth magnets. However, adopting rare-earth magnets brings strong stray fields, causing an electromagnetic interference (EMI) problem. In this study, patterned CoNiP hard magnets were electrodeposited on flexible substrates through microfabrication. Origami magnetization was utilized to control the resultant stray fields and thus the pole piece of CoNiP magnets can successfully trigger the output of the Wiegand pulse. In comparison, the output voltage of the triggered pulse acquired through the patterned CoNiP magnets is comparable to that acquired by using the rare-earth magnets. Furthermore, both the volume (and hence the weight) of the Wiegand sensor and the EMI issue can be significantly reduced and mitigated, respectively, by the CoNiP magnets.

Development of a Process to Recycle NdFeB Permanent Magnets Based on the CaO-Al2O3-Nd2O3 Slag System

Nd, Pr and Dy are critical raw materials as major components for rare earth permanent magnets (REPM). These are integral for several components placed for example within electric vehicles and wind turbine generators. REE primary production is mainly realized in China (~80%) and no REPM recycling industry has been established. Hydrometallurgical recycling routes lead to iron dissolution (66 wt. % Fe in REPM), while pyrometallurgical approaches that utilize SiO2 risk contaminating the produced iron phase. A two-step process is presented that (i) creates an FeOx-CaO-Al2O3-REE2O3 molten slag at 1500 °C through oxidative smelting and (ii) separates an iron-depleted slag phase (CaO-Al2O3-REE2O3) and a molten iron phase via carbothermic or metallothermic reduction at 1700–2000 °C. The slag has been designed as a selective collector phase and the REE2O3 loading within the bulk slag can reach up 25 wt. % REE2O3 at 1700 °C. The contained minerals within the slag exhibit >40 wt. % REE (a higher REE concentration than in the initial REPM). The resulting phases are characterized via ICP-OES, CS and SEM-EDX. In addition, the first results with regard to the downstream hydrometallurgical processing of the CaO-Al2O3-REE2O3 slag are presented aiming at the recovery of REE2O3, as well as of CaO and Al2O3. The latter compounds are to be reused during the first process step, i.e., the oxidative smelting of REPM. Slag leaching with methane sulfonic acid (MSA) and separation with alternative methods, such as solvent extraction, seems promising. Future work will include slag filtration with the aim to separate REE-rich solid phases (minerals) from the slag and also molten salt electrolysis of the produced REE2O3 oxides.

Role of natural deep eutectic solvents (NADESs) in coagulation bath for PVDF-based membranes on enhanced permeation and separation of rare earth ions

Efficient separation of single rare earth element such as neodymium (Nd) has become an important research topic due to the supply crisis which seriously restricts the application and promotion of rare earth permanent magnets. PVDF-based separation membranes prepared by non-solvent induced phase separation (NIPS) method usually exhibited hydrophobic surface properties resulting in performance attenuation and operation cost increase. This article applied an easily available NADES from betaine and lactic acid to regulate and control the coagulation bath of a polymer inclusion membrane (PIM) for the separation of Nd, Sm and Dy ions. Evidences for the formation of DES were characterized via 1H NMR and FT-IR, and betaine showed more obvious changes than lactic acid during the formation of DES via hydrogen bonds. With the help of DES, pores on the surface were much larger and richer, and the migration of PO and P–O groups to the lower epidermal layer of the membrane made the surface layer become more hydrophilic. DES accelerated the liquid-liquid demixing process and led to faster membrane-forming speed and typical finger-like macrovoids and short vertical penetration channels, which could be observed at high DES contents, and a DES content of 5 wt% was found the most optimal considering the overall permeability and separation performances. As an effective means to improve membrane's performances, adding hydrophilic NADESs at a proper ratio in the coagulation bath would be conducive to form more porous structures, higher surface hydrophilicity, optimized permeability and separation performances.

Temperature dependence of semi-hard iron silicide rare-earth free magnet

Searching for rare-earth free permanent magnet attracts extensive research interests due to diverse technological applications and other subtle issues. Here, the temperature dependent magnetic properties of Fe5SiC structure are explored. The Fe5SiC has a critical temperature of 710 K with perpendicular magnetic anisotropy. The magnetic anisotropy constant and coercive field are monotonically decreased with increasing temperature. For instance, the magnetic anisotropy constant is 0.42 MJ m−3 at zero Kelvin and reduced to 0.24 MJ m−3 and 0.06 MJ m−3 at 300 K and 600 K. The coercive field becomes 0.7 T at 0 K. With increasing the temperatures, it is suppressed to 0.42 T and 0.20 T at 300 K and 600 K, respectively. Overall, the Fe5SiC system has a (BH)max of 417 kJ m−3 at zero Kelvin. The (BH)max is decreased at high temperature. Nonetheless, we obtain the (BH)max of 234 kJ m−3 at 300 K. Since the Fe5SiC shows better permanent magnetic (PM) property than the conventional ferrites and also CeCo5. This finding may indicate that the Fe5SiC can be a potential candidate as a Fe-based gap PM between ferrite and Nd–Fe–B (or Sm–Co) at room temperature.

Magnetic Pole Equivalence and Performance Analyses of Multi-Layer Flux-Barrier Combined-Pole Permanent-Magnet Synchronous Machines Used for Electric Vehicles

Multi-layer flux-barrier combined-pole permanent-magnet synchronous machines (MLFB-CP-PMSMs) are especially suitable for machines used in electrical vehicles (EVs), as they represent a tradeoff between electromagnetic performance and the consumption of high-priced rare-earth permanent magnets (PM). In this paper, magnetic pole equivalence and performance analyses of the MLFB-CP-PMSM are investigated. Firstly, three types of PM arrangements of combined poles are introduced, namely, parallel, series and series–parallel. Then, the magnetic circuit model and magnetic pole equivalence principle of MLFB-CP-PMSMs with different PM arrangements are analyzed. After that, the accuracy of the equivalence method is studied by comparing the machine electromagnetic performance before and after equivalence. Finally, the MLFB-CP-PMSM’s performance, including the loss, efficiency and electromagnetic torque, is analyzed. The results prove that the MLFB-CP-PMSM has the advantage of high efficiency, and the equivalence method can retain precision when the MLFB-CP-PMSM armature reaction degree varies.

A core–shell magnet Mn70Bi30 grown at seeds in magnetic fields and its impacts on its spin-dynamics, Curie point and other tailored properties

The MnBi alloys is a model series of rare-Earth free magnets for surge of technologies of small parts of automobiles, power generators, medical tools, memory systems, and many others. The magnetics stem primarily at unpaired Mn-3d5 spins (a 4.23 μ B moment) align parallel via an orbital moment 0.27 μ B of Bi-5d106s2p3 in a crystal lattice. Thus, using a surplus Mn (over Bi) in a Mn70Bi30 type alloy designs a spin-rich system of duly tailored properties useful for magnetics and other devices. In this view, we report here a strategy of a refined alloy powder Mn70Bi30 can grow into small crystals of hexagonal (h) plates at seeds as annealed in magnetic fields (in H2 gas). So, small h-plates (30 to 50 nm widths) are grown up at (002) facets, wherein the edges are turned down in a spiral (≤2.1 nm thicknesses) in a core–shell structure. The results are described with x-ray diffraction, lattice images and magnetic properties of a powder Mn70Bi30 (milled in glycine) is annealed at 573 K for different time periods, so to the Mn/Bi order at the permeable facets (seeds). Duly annealed samples exhibit an enhanced magnetization, M s → 70.8 emu g−1, with duly promoted coercivity H c → 10.810 kOe (15.910 kOe at 350 K), energy–product 14.8 MGOe, and the crystal-field-anisotropy, K 1 → 7.6 × 107 erg cm−3, reported at room temperature. Otherwise, M s should decline at any surplus 3d5-Mn spins order antiparallel at the antisites. Enhanced Curie point 658.1 K (628 K at Mn50Bi50 alloy) anticipates that a surplus Mn does favor the Mn–Bi exchange interactions. Proposed spin models well describe the spin-dynamics and lattice relaxations (on anneals) over the lattice volume (with twins) and spin clusters.

Effects of rare-earth magnetism on the superconducting upper critical field in infinite-layer nickelates.

The search for superconductivity in infinite-layer nickelates was motivated by analogy to the cuprates, and this perspective has framed much of the initial consideration of this material. However, a growing number of studies have highlighted the involvement of rare-earth orbitals; in that context, the consequences of varying the rare-earth element in the superconducting nickelates have been much debated. Here, we show notable differences in the magnitude and anisotropy of the superconducting upper critical field across the La-, Pr-, and Nd-nickelates. These distinctions originate from the 4f electron characteristics of the rare-earth ions in the lattice: They are absent for La3+, nonmagnetic for the Pr3+ singlet ground state, and magnetic for the Nd3+ Kramer's doublet. The unique polar and azimuthal angle-dependent magnetoresistance found in the Nd-nickelates can be understood to arise from the magnetic contribution of the Nd3+ 4f moments. Such robust and tunable superconductivity suggests potential in future high-field applications.

Beyond 15 MW: A cost of energy perspective on the next generation of drivetrain technologies for offshore wind turbines

Leading wind turbine manufacturers are racing to build larger and more powerful offshore machines. Drivetrain configurations often use a permanent-magnet synchronous generator (PMSG), in either a direct-drive configuration or coupled to a gearbox. With increasing demand for critical rare-earth magnets, new generator technologies are emerging to ensure a stable and secure supply chain. We evaluate three different topologies of radial flux synchronous generators employing high field magnets with reduced or no rare-earth content: a direct-drive interior PMSG (DD-IPMSG), a geared drivetrain combining a medium speed gearbox with a PMSG (MS-PMSG), and a direct-drive low-temperature superconducting generator (DD-LTSG). We develop a conceptual design module for each of these technologies within a larger framework for full turbine design. This provides the fairest comparison between technologies at nominal power ratings from 15–25MW, which represent the next generation of offshore wind turbines. The analyses show that if operational expenditures (OpEx) are constant across the technologies, MS-PMSG results in the lowest LCOE with reductions of up to 7% relative to DD-IPMSG. DD-LTSG also yields lower LCOE values by 2%–3% for fixed-bottom turbines and 3%–5% with a floating platform. However, results are sensitive to OpEx assumptions, with a mere 10% increase causing the conclusions to shift.

A combined-pole permanent magnet synchronous motor incorporating nanocomposite magnets

The development of rare earth permanent magnet materials has made outstanding contributions to the advancement of high performance permanent magnet synchronous motors (PMSM). However, the non-renewable and strategic protection of rare earth resources leads to price fluctuations and supply risk of rare earth permanent magnets, limiting electrical vehicle development and popularity. In this paper, we optimized the design of the nanocomposite magnet microstructure and proposed a combined-pole interior nanocomposite permanent magnet synchronous motor (CP-INPMSM), combining nanocomposite magnet and PMSM. The simulation results show that the no-load back-electromotive force and torque of the motor are improved. This design can reduce the usage of rare-earth permanent magnet materials and improve the electromagnetic performance of the motor.

Clinical Presentation and Outcome of Multiple Rare Earth Magnet Ingestions in Children of Qatar. A Single-Center Experience.

Rare earth magnets are powerful magnets that can have several negative effects if ingested. The goal of our study is to describe the result of multiple rare earth magnets ingested by children in Qatar. This is observational research. We conducted a retrospective chart review and descriptive analysis of all cases of multiple rare earth magnetic ingestion that werepresented to the Emergency Department of Sidra Medicine between January 2018 and July 2022. We obtained an exemption for this study from our institutional review board (IRB). In our research, we identified 21 children having multiple rare earth magnetic ingestions. The predominant symptoms were abdominal pain and vomiting which were observed in 57% (n=12) and 48% (n=10) of the patients respectively. The most common sign was abdominal tenderness,observed in 14% (n=3) of the patients. In our sample, 38% (n=8) of the patients were managed conservatively whereas 62% (n=13) needed intervention. In our study, 48% (n=10) of the patients sustained complications. The frequent complications were intestinal perforation appreciated in 24% (n=5) and intestinal perforation with fistula formation in 19% (n=4) of the patients. The median age of these patients was two years while the median number of magnets ingested was six. The ingestions were unwitnessed, and the duration of ingestions was unknowninthemajorityofpatientswhoexperiencedcomplications (n=8/10). If numerous rare earth magnetis ingested, children are in high danger of harm. It can be difficult to pinpoint the cases in younger children due to poor communication skills, especially if the intake is unreported. Although Qatar has established restrictions banning the import of rare earth magnets, there are reported cases of children with rare earth magnets ingestions.

Tunable spin texture transformation with field-free biskyrmion over a broad temperature range in rare-earth ferrimagnets

Exploring and discovering various types of skyrmions has enriched the fundamental study and the active skyrmionics aiming at using skyrmions in spintronics due to the advantages of global stability as high-density magnetic information bit. The unique capability to introduce abundant spin structures, physical phenomena, and dynamics due to the interactions of 4f and 3d electrons push the rare-earth–transition metal (RE–TM) magnets into the research frontier again. Herein, the exotic magnetic domain configurations are discovered in traditional ThMn12-type RE–TM magnets. It is clearly demonstrated that the magnetic anisotropy alteration and magnetic coupling between the respective RE and TM sublattices are responsible for the abundant magnetic domain evolution. In particular, the field-free biskyrmions at room temperature and tunable spin texture transformation are successfully obtained via manipulating the in-plane magnetic anisotropy, which has broadened the physical mechanism and application exploration of manipulating ferrimagnetic order to generate topological spin structures in strategic rare-earth magnets.

Energy Efficiency Improvement of Electric Machines without Rare-Earth Magnets

Electric motors are one of the largest consumers of electricity and are responsible for 40–45% of the world’s energy consumption [...]

Design of Glass Fiber-Doped High-Resistivity Hot-Pressed Permanent Magnets for Reducing Eddy Current Loss

The Nd-Fe-B hot-deformation magnet with high resistivity was successfully prepared by hot-pressing and hot-deformation of Nd-Fe-B fast-quenched powder with amorphous glass fiber. After the process optimization, the resistivity of the magnet was increased from 0.383 mΩ·cm to 7.2 mΩ·cm. Therefore, the eddy current loss of magnets can be greatly reduced. The microstructure shows that the granular glass fiber forms a continuous isolation layer during hot deformation. At the same time, the boundary of Nd-Fe-B quick-quenched the flake and glass fiber from the transition layer, which improves the binding of the two, and which can effectively prevent the spalling of the isolation layer. In addition, adding glass fiber improves the orientation of the hot deformation magnet to a certain extent. The novel design concept of insulation materials provides new insights into the development and application of rare earth permanent magnet materials.

Production cost modeling for permanent magnet synchronous machines for electric vehicles

A cost model for the estimation of production costs of permanent magnet synchronous machines (PMSM) is presented, which allows to alter design choices such as wire technology, winding layout, cooling system, materials and more. With the goal to make results reproducible by others, the methods are explained in detail and used data and assumptions are given. The developed model helps to understand the interaction between the design of PMSM, manufacturing methods and the resulting costs. With it, different PMSM technologies and materials can be evaluated regarding its influence on the production costs, which is a perquisite to find the best compromise between performance and costs. Production volume is shown to be the most decisive factor for the resulting production costs. Between minimum and maximum assumed volumes, an average cost per unit reduction of 67% could be observed. Furthermore, the results imply that the winding production is responsible for the greatest part of the overall costs, followed by the rotor assembly (including rare earth magnets). When using the model to compare different wire types, it can be stated that up to a production volume of roughly 150,000 units/year, hairpin wires are more expensive to produce. Above this volume, hairpin windings will get cheaper than round wire windings due to its higher grade of automation of the production process. Through the conducted investigations and the presented results, it is demonstrated that the cost model can serve to evaluate technologies with regards to costs in the early development stage. This way a more holistic assessment of technologies for PMSM is possible, helping to find the ideal compromises between costs and performance and to increase the attractiveness of sustainable mobility.

Subphase exploration for SmFe12-based permanent magnets by Gibbs energies obtained with first-principles cluster-expansion method

In the development of SmFe12-based rare-earth permanent magnets, it is yet to establish a pathway to liquid-phase sintering producing nonmagnetic grain-boundary subphases. Here, phase equilibria of the Sm-Fe-Cu ternary system are examined computationally to explore such a pathway and grain-boundary subphases of SmFe12-based magnets through Gibbs free energies for various phases. A key quantity, the mixing enthalpy is examined from first principles. We show that the B2 Sm-Cu-Fe is a candidate for a nonmagnetic subphase, where the solubility of Fe into Sm-Cu is better described by the cluster-expansion method finding attractive Cu-Fe interaction within the B2 sublattice. In addition, it is found that the liquid phase of Sm-Cu slightly including Fe directly equilibrates with SmFe12, which is consistent with experiments. We point out the possibility of liquid-phase sintering of the SmFe12-based magnets using this liquid phase without significant composition changes by the solidification. The mechanism of attractive interaction between Fe and Cu in B2 Sm(Cu, Fe) is clarified from the viewpoint of electron theory.