Rare-earth Magnets Research Articles

Revisiting the assessment of magnetic texture of Rare-Earth Magnets: The role of coercivity

A crucial figure of merit of rare-earth magnets is their magnetic texture, because it is closely related to the maximum remanence a magnet can achieve, hence assessing the magnetic texture is pivotal in terms of magnet’s performance. Fernengel et al. (1996) developed a methodology based on magnetometry, which allows for a quick determination of the texture by calculating the degree of alignment 〈cosθ〉 from the remanent magnetization in directions parallel and perpendicular to the texture axis of the magnet. Although this method provided reliable values, its application was limited to magnets with high degrees of alignment (〈cosθ〉 > 95 %), a restriction that was corrected by Quispe et al. (2020). Nevertheless, recent experiments have indicated that the magnetometry technique can introduce errors in texture assessment when the magnet presents high levels of coercivity. This work presents an approach that incorporates a correction factor into the magnetometry technique, accounting for the effect of the coercivity and circumventing this error source in texture assessment. The proposed methodology has been successfully applied to magnets with varying levels of coercivity.

Study on color separation and identification technology for rare-earth permanent magnet waste

Study on color separation and identification technology for rare-earth permanent magnet waste

Doping effects in strontium hexaferrite: Theoretical and experimental analysis

Hexagonal ferrites based on SrFe12O19 (SFO) are vital materials in the field of permanent magnets, valued for their cost-effectiveness and reliable magnetic properties, making them a more affordable alternative to rare-earth permanent magnets. This study focuses on understanding the doping effects of commonly used elements in SFO system. DFT calculation results show that doping La or La-Co can enhance the phase stability of SFO, in which Co has a preference for the 4f1 sites of Fe. The total magnetic moment was observed to slightly decrease with La doping, whereas it exhibited an increasing trend with La-Co and La-Ca-Co co-doping and the largest increase of 6.5 % can be obtained in Sr2LaCaFe44Co4O76 (SLCFCO). The increase in the total magnetic moment is mainly attributed to the smaller antiferromagnetic moment of Co than that of Fe on 4f1 sites, as well as the reduction in the antiferromagnetic Fe moments at 4f1 and 4f2 sites. The total density of states indicates a transition from semiconductor behavior to a metallic character both in the La-Co and La-Ca-Co doped versions. The experimental results validate the theoretical predictions, confirming enhancements in magnetic performance. The saturation magnetization increased from 63.86 Am2/kg in SrFe11.7O19 (SFO) to 67.53 Am2/kg in Sr0.4La0.4Ca0.2Fe10.5Co0.5O19 composition. These findings provide a vital understanding of tuning the magnetic and electronic properties in doped SFO, which will enable the development of advanced applications in magnetic materials.

Unraveling Magnet Structural Defects in Permanent Magnet Synchronous Machines—Harmonic Diagnosis and Performance Signatures

Rare-earth-based permanent magnets (PMs) have a vital role in numerous sustainable energy systems, such as electrical machines (EMs). However, their production can greatly harm the environment and their supply chain monopoly presents economic threats. Alternative materials are emerging, but the use of rare-earth PMs remains dominant due to their exceptional performance. Damage to magnet structure can cause loss of performance and efficiency, and propagation of cracks in PMs can result in breaking. In this context, prolonging the service life of PMs and ensuring that they remain damage-free and suitable for re-use is important both for sustainability reasons and cost management. This paper presents a new harmonic content diagnosis and motor performance analysis caused by various magnet structure defects or faults, such as cracked or broken magnets. The proposed method is used for modeling the successive physical failure of the magnet structure in the form of crack formation, crack growth, and magnet breakage. A surface-mounted permanent magnet synchronous motor (PMSM) is studied using simulation in Ansys Maxwell software (Version 2023), and different cracks and PM faults are modeled using the two-dimensional finite element method (FEM). The frequency domain simulation results demonstrate the influence of magnet cracks and their propagation on EM performance measures, such as stator current, distribution of magnetic flux density, back EMF, flux linkage, losses, and efficiency. The results show strong potential for application in health monitoring systems, which could be used to reduce the occurrence of in-service failures, thus reducing the usage of rare-earth magnet materials as well as cost.

Tunning Pr to achieve ultra-high magnetic properties of anisotropic nanocrystalline (Sm,Pr)Co5 magnets

In this study, we reported on the bulk anisotropic nanocrystalline Sm1-xPrxCo5 (x = 0.2–0.6) magnets aimed at achieving excellent energy products. Through a combination of advanced processing techniques, including melt spinning, hot pressing, and hot deformation process, bulk magnets with a fine nanocrystalline structure were successfully synthesized. The results revealed that the substitution of Pr strengthened the c-axis texture and the saturation magnetization, facilitating the enhancement of remanence (Mr) and maximum magnetic energy product [(BH)max]. However, Pr substitution decreased the coercivity (Hci) due to the reduced magnetocrystalline anisotropy field. Excellent magnetic properties are obtained for Sm0.4Pr0.6Co5 magnets with the (BH)max of 23.2 MGOe and Hci of 11.8 kOe. The prepared (Sm,Pr)Co5 magnets with different Pr contents have essentially the same microstructure with RECo5 main phase grains of about 400 nm in diameter and fine dispersed rare earth-rich nanoprecipitates. Our findings can provide reliable reference for manufacturing nanocrystalline permanent magnet materials and promote the development of rare earth permanent magnet new materials.

Topological magnetic defects in a strong permanent magnet Nd2Fe14B

Skyrmions, highly mobile and manipulable magnetic objects, have garnered significant interest for their potential applications in modern magnetic device technology. However, their formation has been limited to a small number of materials due to the delicate balance of magnetic energies involved. In this study, we report the irreversible formation of skyrmions in Nd2Fe14B, a rare-earth permanent magnet characterized by large magnetic anisotropy. Remarkably, these magnetic topological defects exist over a wide range of temperatures and magnetic fields (295–565 K and 0–0.1 T) due to the high Curie temperature and significant magnetic anisotropy of Nd2Fe14B. Our findings not only unveil a new material where skyrmions can form but also open up possibilities for exploring topological defects in various magnetic systems, including strong hard magnets.

Exploring rare-earth Kitaev magnets by massive-scale computational analysis

The Kitaev honeycomb model plays a pivotal role in the quest for quantum spin liquids, in which fractional quasiparticles would provide applications in decoherence-free topological quantum computing. The key ingredient is the bond-dependent Ising-type interactions, dubbed the Kitaev interactions, which require strong entanglement between spin and orbital degrees of freedom. Here we investigate the identification and design of rare-earth materials displaying robust Kitaev interactions. We scrutinize all possible 4f electron configurations, which require up to 6+ million intermediate states in the perturbation processes, by developing a parallel computational program designed for massive-scale calculations. Our analysis reveals a predominant interplay between the isotropic Heisenberg J and anisotropic Kitaev K interactions across all realizations of the Kramers doublets. Remarkably, instances featuring 4f3 and 4f11 configurations showcase the prevalence of K over J, presenting unexpected prospects for exploring the Kitaev quantum spin liquids in compounds, including Nd3+ and Er3+, respectively.

Exploring the structural, optical, dielectric and magnetic properties of rare earth samarium doped Ca-Mg based Ca0.5Mg0.5Fe12−xSmxO19 ferrite nanoparticles

The emergence of M-type hexaferrite presents an encouraging alternative to rare earth magnets, due to its economic feasibility and outstanding magnetic properties. This makes it a viable option for applications in the electric automotive and magnetic industry applications. In this study, we utilized a sol–gel auto-combustion technique to synthesize a series of samarium (Sm) doped calcium-magnesium (Ca-Mg) hexaferrite samples having chemical formula Ca0.5Mg0.5Fe12−xSmxO19 (x = 0.00, 0.05, 0.10, 0.15, and 0.20). The XRD analysis confirmed the crystal structure of the synthesized materials, revealing a consistent magneto-plumbite phase across all samples. Scanning electron microscopy (SEM) investigations further confirmed the homogeneous distribution and agglomeration of nanostructures. FTIR analysis identified the presence of two primary absorption bands in Ca-Mg hexaferrites with both bands exhibiting a shift towards lower frequency ranges with increasing doping levels. The dielectric loss (ε″) and dielectric constant (ε′) were higher at lower frequencies but decreased as the frequency increased. Additionally, higher concentrations of samarium resulted in further reductions in both dielectric loss (ε″) and dielectric constant (ε′). Notably, saturation magnetization (Ms) and remanence (Mr) values demonstrated an increasing trend with higher degrees of Sm+3 substitution, while coercivity (Hc) values exhibited relative stability. Our findings indicate that these materials possess promising magnetic parameters falling within the ranges of 31.52–37.77 emu·g−1 for Ms, 18.16–21.53 emu·g−1 for Mr, and 2.088–2.243 kOe for Hc, suggesting their potential utility across diverse applications including permanent magnets used in electric vehicle motors, storage devices, microwave components, and electromagnetic radiation absorbers.

Computational Investigation on the Structural, Electronic and Magnetic Properties of Si-Doped L10 FeNi Alloy for Clean Energy

For the first time, this study conducts a computational analysis by employing density functional theory (DFT) to investigate the effects of silicon doping as substitutional defects on the structural, electronic, and magnetic characteristics of the L10-FeNi alloy. The aim of this study was to explore the potential applications of Si-doped FeNi compounds as alternatives to rare-earth permanent magnets. For this, we have performed full potential calculations of L10-FeNi with substitutional Si-doping within a generalized gradient approximation. Two types of substitutional Si-doping (ONi/OFe) in the Ni/Fe site of the parent alloy have been investigated. The computed formation energy (Ef) indicates that the incorporation of silicon defects increases the structural stability of tetragonally distorted L10-FeNi. Moreover, our findings demonstrate that the FeNi:Si(ONi) in the L10-structure has a stable saturation magnetization (Ms), whereas the FeNi:Si (OFe) has a small reduction in Ms. Therefore, Si-substituted FeNi alloys can be tuned to become a good candidate for permanents magnets.

Magnetic Attachment For Tooth Supported Mandibular Overdenture: A Case Report

The goal of preventive prosthodontics is to highlight the significance of any surgery that can postpone or completely prevent future prosthodontic issues. In terms of preventive prosthodontics, the overdenture is a therapeutic option that is supported by science. Overdentures have been fitted with a variety of attachments to improve retention. Because rare earth magnets like Sm-Co and Nd-Fe-B may be produced in small sizes as retentive devices for complete dentures, detachable partial dentures, obturators, and maxillofacial prosthesis, their application for increasing retention has been widely used in the field of prosthodontics. This article presents a simple method of fabricating mandibular over denture retained by magnets in a patient whose mandibular residual ridge was severely resorbed with few remaining teeth and opposed by maxillary complete denture

PMSM Design for Elevators: Determination of the Basic Topology Affecting Performance

In recent years, with the increase in high-rise building construction, there has been a rise in demand for elevators. This demand has spurred mutual growth between the vertical transportation sector and high-rise building construction. Both sectors are improving technology, security, and comfort standards. Traditional elevator traction machines typically employ asynchronous motors coupled with geared reducers, despite their low energy efficiency and requirement for large machine rooms. However, with the proliferation of rare-earth magnet materials and advancements in driver technologies, the use of Permanent Magnet Synchronous Motors (PMSMs) in elevator traction machines has increased. PMSMs operate with direct drive, eliminating the need for reducers. High efficiency and passenger comfort are crucial parameters for elevator traction machines. This study focuses on identifying the fundamental topology that could influence the performance of PMSMs for gearless elevator machines. Factors such as stator materials, rotor structures, permanent magnets, winding configurations, slot/pole combinations, cogging torque and torque ripple have been examined to select suitable design topologies for elevator motors. Important topics such as the magnetic properties of grain-oriented silicon steel sheets used in stator construction, B-H curves, lamination forming and stacking factors have been addressed. Two different rotor topologies and magnet arrangements, namely internal and external, have been investigated in PMSM designs. Additionally, the use of four different magnet materials, namely AlNiCo, Ferrite, NdFeB, and SmCo have been compared for PMSM traction motors in elevators. Single-layer and double-layer winding configurations, distributed and concentrated winding configurations have been compared. Fractional slot/pole combinations, which directly affect the performance and comfort of PMSMs, have also been examined based on information obtained from the literature. Particularly, structures with high winding factors, such as 12/10, 12/14, 18/16, 18/20, 24/22, and 24/26 have been identified. Finally, studies on skewing to reduce cogging torque and torque ripple have been addressed.

Mapping complexity: Analyzing rare earth production life cycle inventories with network analysis

Understanding the significance of process clusters in life cycle inventory networks is crucial for optimizing supply chains, especially for critical elements like rare earth elements (REEs) production. This study employs network analysis (NA) to examine life cycle networks using facility-level energy/material data, extracting information from LCA networks. Based on Chinese facility reports, the investigation evaluates the environmental footprint of various rare earth production pathways, vital to the clean energy sector. It also considers rare earth permanent magnet manufacturing and magnet recycling. Using network metrics, including indegree/outdegree strength, closeness centrality, and betweenness centrality, the study assesses the resilience and sustainability of REEs production networks. Results highlight vulnerable nodes like "Neodymium Oxide" and "Nd Metal," aiding in identifying environmentally impactful materials and energy flows to develop more sustainable processes for meeting growing demand while enhancing environmental performance.

Effect of element doping on the structural stability, magnetic properties and electronic structure of SmCo5-based rare earth permanent magnets

Doping transition metals has been proven as an effective method to enhance the performance of Sm-Co based rare earth permanent magnets. However, due to the complex interactions involved, the specific effects on magnetic properties, atomic occupancy preferences and structural stability mechanisms are still to be further investigated. In this study, we systematically investigated the influence of various transition metal dopants on the structural stability, magnetic properties and electronic structure of SmCo5 rare earth permanent magnet using first-principles calculations. Our calculations show that Ti, V, Cr, Mn, Ni, Cu, Zn elements preferentially occupy the 3 g site, while Sc and Zr tend to occupy the 1a site, and Fe elements have a preference for the 2c site. Regarding structural stability, doping with Sc, Cr, Mn, Fe, Ni, Cu, Zn and Zr all contribute to enhancing structural stability, while Ti and V doping exhibit adverse effects. Magnetic calculations indicate that doping with Mn and Fe significantly increases the total magnetic moment of the SmCo5 system. Notably, at a high doping concentration of 60 at%, the Ni and Zn-doped systems exhibit an exceptionally large magnetocrystalline anisotropy energy Additionally, a change in the magnetic easy axis direction occurs when the doping concentrations of Cr, Fe, Cu and Zn reach 60 at%, 40 at%, 40 at% (and 60 at%), 40 at% (and 60 at%), respectively. Our work provides important theoretical guidance for further optimizing the performance of Sm-Co based rare earth permanent magnets.

A NOVEL MAGNETIC SYSTEM TO TREAT TOTAL HIP ARTHROPLASTY INSTABILITY

Dislocation after total hip replacement (THR) is a devastating complication. Risk factors include patient and surgical factors. Mitigation of this complication has proven partially effective. This study investigated a new innovating technique to decrease this problem using rare earth magnets.Computer simulations with design and magnetic finite element analysis software were used to analyze and quantitate the forces around hip implants with embedded magnets into the components during hip range of motion. N52 Neodymium-Iron-Boron rare earth magnets were sized to fit within the existing acetabular shells and the taper of a hip system. Additionally, magnets placed within the existing screw holes were studied. A 50mm titanium acetabular shell and a 36mm ceramic liner utilizing a taper sleeve adapter were modeled which allowed for the use of a 12mm × 5mm magnet placed in the center hole, an 18mm × 15mm magnet within the femoral head, and 10mm × 5mm magnets in the screw holes.Biomechanical testing was also performed using in-vitro bone and implant models to determine retention forces through a range of hip motion.The novel system incorporating magnets generated retentive forces between the acetabular cup and femoral head of between 10 to 20 N through a range of hip motion. Retentive forces were stronger at the extreme position hip range of motion when additional magnets were placed in the acetabular screw holes. Greater retentive forces can be obtained with specially designed femoral head bores and acetabular shells specifically designed to incorporate larger magnets. Mechanical testing validated the loads obtained and demonstrated the feasibility of the magnet system to provide joint stability and prevent dislocations.Rare earth magnets provide exceptional attractive strength and can be used to impart stability and prevent dislocation in THR without the complications and limitations of conventional methods.

Soft X-Ray Phase Nanomicroscopy of Micrometer-Thick Magnets

Imaging of nanoscale magnetic textures within extended material systems is of critical importance to both fundamental research and technological applications. While high-resolution magnetic imaging of thin nanoscale samples is well established with electron and soft x-ray microscopy, the extension to micrometer-thick systems currently requires hard x rays, which limits high-resolution imaging to rare-earth magnets. Here, we overcome this limitation by establishing soft x-ray magnetic imaging of micrometer-thick systems using the pre-edge phase x-ray magnetic circular dichroism signal, thus making possible the study of a wide range of magnetic materials. By performing dichroic spectroptychography, we demonstrate high spatial resolution imaging of magnetic samples up to 1.7 μm thick, an order of magnitude higher than conventionally possible with soft x-ray absorption-based techniques. We demonstrate the applicability of the technique by harnessing the pre-edge phase to image thick chiral helimagnets, and naturally occurring magnetite particles, gaining insight into their three-dimensional magnetic configuration. This new regime of magnetic imaging makes possible the study of extended non-rare-earth systems that have until now been inaccessible, including magnetic textures for future spintronic applications, non-rare-earth permanent magnets for energy harvesting, and the magnetic configuration of giant magnetofossils. Published by the American Physical Society 2024

Comparison between a surface permanent magnet synchronous motor and a segmented stator switched reluctance motor with aluminum windings for light electric traction

Nowadays, light electric vehicles are usually powered by drives with motors that use rare-earth permanent magnets. Nevertheless, due to the problems these materials present, light electric vehicle manufacturers are open to considering other alternative drives free of permanent magnets. This paper raises a comprehensive comparison between a surface permanent magnet synchronous motor and a segmented stator switched reluctance motor with aluminum windings for light electric traction, specifically for a motorcycle similar to the Super Soco TCmax.

Hard Magnetic FePt Nanoparticles within Nanostructured Silicon to Improve the Maximum Energy Product

In this work nanostructured silicon, silicon nanotubes (SiNTs) and porous silicon (PSi), with embedded hard magnetic FePt nanoparticles (NPs) is used as platform to create nanomagnet-arrays. The magnetic response of FePt-loaded composite materials is investigated, which have potential in high-performance magnets and as rare earth magnet alternatives. PSi/FePt demonstrates superior hard magnetic behavior with a higher coercivity and remanence compared to SiNTs/FePt. Varying the Fe molar ratio in deposits results in a small coercivity range. FePt-loaded samples consistently show increased coercivity and remanence compared to Co-loaded samples, with PSi exhibiting a stronger effect compared to SiNTs.The fabrication of the PSi samples was performed by anodization of p+ silicon in a 5 wt% HF solution. A current density of 50 mAcm-2 was applied during the etching. The samples offer an average diameter of 50 nm. The SiNTs were produced by using arrays of ZnO nanowires (NWs) as template, followed by Si deposition and finally etching off the ZnO NWs which is described in (1). FePt nanocrystals were formed within the SiNTs by a multistep process, consisting of soaking previously APTES functionalized SiNTs in a solution containing 0.1 mM Citric acid, 0.5 mM of H2PtCl6 6H2O, and depending on the given ratio 0.5-1.5 mM of Fe(NO3)3 9H2O. The samples were dried in a vacuum oven, followed by a heat treatment at 500° C for 1 hr in Ar atmosphere, then the samples were washed several times with water and ethanol. In a similar way FePt NPs were formed in PSi samples, however PSi did not receive the APTES functionalization before the solution soaking.For these samples, the average FePt particle size is 5 (± 2) nm in SiNTs samples and 9 (± 4) nm for the particles inside PSi, however it should be pointed out that the FePt ratios calculated from reactants was different than the ratios determined from EDX experimental data. The calculated stoichiometry of Pt:Fe (based on reactant concentrations) of 1:1, 1:3 and 1:6 was experimentally determined values via EDX to be 10:1, 1.6:1 and 0.5:1 for SiNTs; for the corresponding PSi samples of calculated 1:3 and 1:6 ratios was experimentally 40:1 and 10:1.Magnetization measurements were carried out by VSM in recording the magnetic response dependent on the magnetic field. Samples with different Fe content (Pt:Fe = 1:1, 1:3, 1:6) offer a variation of the coercivity in the range of 5% for both types of matrices (SiNTs, PSi). Furthermore the investigations show that the coercivities of PSi loaded with FePt NPs is about twice the coecivities of SiNTs loaded with FePt NPs. SiNTs/FePt samples with a ratio Pt:Fe 1:6 offer a coercivity of about 240 Oe and PSi/FePt offers a coercivity more than twice as high of about 560 Oe.Comparing the FePt loaded samples with samples loaded with Co NPs, in both sample types an increase of the coercivity is observed for FePt. Also in the case of Co-loading the utilization of PSi as template offers higher coercivities compared to SiNTs as template. From the investigated composite systems the ones consisting of PSi and FePt offer the highest energy product.(1) Huang, X., Gonzalez-Rodriguez, R., Rich, R., Gryczynski, Z., Coffer, J.L., Chem. Comm. 2013, 49, 5760.

Fast fabrication of a hierarchical nanostructured multifunctional ferromagnet.

Materials with multifunctionality affect society enormously. However, the inability to surmount multiple functionality trade-offs limits the discovery of next-generation multifunctional materials. Departing from conventional alloying design philosophy, we present a hierarchical nanostructure (HNS) strategy to simultaneously break multiple performance trade-offs in a material. Using a praseodymium-cobalt (PrCo5) ferromagnet as a proof of concept, the resulting HNS outperforms contemporary high-temperature ferromagnets with a 50 to 138% increase in electrical resistivity while achieving their highest energy density. Our strategy also enables an exceptional thermal stability of coercivity (-0.148%/°C)-a key characteristic for device accuracy and reliability-surpassing that of existing commercial rare-earth magnets. The multifunctionality stems from the deliberately introduced nanohierarchical structure, which activates multiple micromechanisms to resist domain wall movement and electron transport, offering an advanced design concept for multifunctional materials.

Microstructural and Magnetic Properties of Nanocrystalline Nd-Fe-B Rare Earth Magnet Prepared by Spark Plasma Sintering Technique

Microstructural and Magnetic Properties of Nanocrystalline Nd-Fe-B Rare Earth Magnet Prepared by Spark Plasma Sintering Technique

A study of rare-earth magnet profiles for torque ripple improvement of axial flux permanent magnet machine

Purpose The purpose of this study is to reduce the cogging torque in axial flux permanent magnet (AFPM) machine using optimal magnet shape. Design/methodology/approach This study analyzes different magnet shapes for AFPM machine performance enhancement. Three-dimensional (3D) finite element analysis is performed to see the effects of pole shaping on the cogging torque of the AFPM machine. Findings The magnetic pole shape has a significant effect on cogging torque and overall efficiency. The conventional model has the highest torque whereas the conventional skewing affected cogging torque positively and significantly reduced the cogging torque. The combination of skewing the pole along with face curving is more effective and decreases the cogging torque from 3.88 Nm to 1.5 Nm. Originality/value Rare-earth magnets are the most expensive and important part of AFPM machines. Shape and volume optimization of rare-earth magnets is crucial for the performance of AFPM machines. The research aims to analyze the different permanent magnet designs for performance improvement of the AFPM machine. Conventional flat top trapezoidal, curved-top and skewed-magnet shapes are analyzed and the performance of the AFPM machine is compared with different magnet shapes. Curved-top shape and skewed magnet significantly reduce the cogging torque. Furthermore, a combination of curved-top shape and skew magnet shape is proposed to reduce the cogging torque further and improve the AFPM machine’s overall performance. Newly proposed magnet profile gives skewed curve magnet shapes which reduce the cogging torque further. 3D finite element analysis has been used to analyze the single-sided AFPM with all four different magnet shapes. The research focuses on single-sided AFPM machines, but the results are also valid for double-sided AFPM machines and can be extended to other topologies of AFPM machines.