United States

Recently, SmFe&lt;sub&gt;11&lt;/sub&gt;Ti-based compounds with the ThMn&lt;sub&gt;12&lt;/sub&gt; crystal structure have been widely studied as a candidate for new permanent magnets due to their excellent intrinsic magnetic properties. Although those compounds have a high anisotropy field (12 T), the actual coercivity is less than 10% of their anisotropy field &lt;sup&gt;1&lt;/sup&gt;. In general, it is well known that fine precipitates corresponding to the size of the domain wall (several nm to several tens of nm) increase the coercivity of hard magnetic materials by acting as the domain wall pinning site. The addition of C to the SmFe&lt;sub&gt;11&lt;/sub&gt;Ti alloy may result in TiC precipitates in the matrix, and subsequent changes in the coercivity can be expected. In this study, SmFe&lt;sub&gt;11&lt;/sub&gt;Ti alloys containing different amount of C atoms were fabricated by the melt-spinning method to investigate the effects of C atoms on the microstructures and magnetic properties.&lt;br/&gt;SmFe&lt;sub&gt;11&lt;/sub&gt;Ti&lt;sub&gt;1+x&lt;/sub&gt;C&lt;sub&gt;x&lt;/sub&gt; (x = 0, 0.05, 0.1, 0.2) alloys with the ThMn&lt;sub&gt;12&lt;/sub&gt; crystal structure was successfully fabricated by the melt-spinning method and subsequent heat treatment. The optimum heat treatment condition was found to be 850°C for 15 minutes, and the coercivity was shown to be about 6.2 kOe regardless of the C content (Fig. 1). In order to understand these results, the microstructural analysis was performed. It was found that the matrix had the ThMn&lt;sub&gt;12&lt;/sub&gt; crystal structure and the average grain size was about 30 nm in all samples regardless of the C content (Fig. 2). In these samples, coarse TiC grains (&amp;gt;100 nm) instead of TiC nano-precipitates were formed independently from the matrix. This result explains the reason why the coercivity did not change. Thus, the experimental conditions for obtaining the precipitates are under investigation.


![](https://assets.underline.io/uploads/markdown_image/1/image/75746d30b79db84128662e894a5853fe.jpg)


Fig. 1 Coercivity measured at 2.5 T of SmFe11Ti1+xCx (x = 0, 0.5, 0.1, 0.2) alloys heat treated at 850°C for 15 minutes.


![](https://assets.underline.io/uploads/markdown_image/1/image/4b02a146f9f1f24e4dc7ba739af1ff8b.png)

Fig. 2 Microstructures of SmFe11Ti1.2C0.2 sample heat treated at 850°C for 15 minutes. (a)Bright field image using Transmission Electron Microscopy. (b)Dark field image and corresponding EDS mapping image using Scanning Transmission Electron Microscopy. The grains which was shown in dark contrast on the image was region that Ti and C was concentrated.


2022 Joint MMM-INTERMAG

The effect of C addition on the magnetic properties and microstructures of nanocrystalline SmFe11Ti alloy

The 15th Joint MMM-INTERMAG Conference (2022 Joint) is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a plenary session, and an evening session, with about 1500 presentations overall. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

The 2022 Joint Conference will offer both in-person and prerecorded on-demand content.

For tickets to the event, please register at the following link: https://magnetism.org/register

Please register for the Joint MMM-Intermag conference to join the event.

This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

Recently, SmFe11Ti-based compounds with the ThMn12 crystal structure have been widely studied as a candidate for new permanent magnets due to their excellent intrinsic magnetic properties. Although those compounds have a high anisotropy field (12 T), the actual coercivity is less than 10% of their anisotropy field 1. In general, it is well known that fine precipitates corresponding to the size of the domain wall (several nm to several tens of nm) increase the coercivity of hard magnetic materials by acting as the domain wall pinning site. The addition of C to the SmFe11Ti alloy may result in TiC precipitates in the matrix, and subsequent changes in the coercivity can be expected. In this study, SmFe11Ti alloys containing different amount of C atoms were fabricated by the melt-spinning method to investigate the effects of C atoms on the microstructures and magnetic properties. SmFe11Ti1+xCx (x = 0, 0.05, 0.1, 0.2) alloys with the ThMn12 crystal structure was successfully fabricated by the melt-spinning method and subsequent heat treatment. The optimum heat treatment condition was found to be 850°C for 15 minutes, and the coercivity was shown to be about 6.2 kOe regardless of the C content (Fig. 1). In order to understand these results, the microstructural analysis was performed. It was found that the matrix had the ThMn12 crystal structure and the average grain size was about 30 nm in all samples regardless of the C content (Fig. 2). In these samples, coarse TiC grains (&gt;100 nm) instead of TiC nano-precipitates were formed independently from the matrix. This result explains the reason why the coercivity did not change. Thus, the experimental conditions for obtaining the precipitates are under investigation.


![](https://assets.underline.io/uploads/markdown_image/1/image/75746d30b79db84128662e894a5853fe.jpg)


Fig. 1 Coercivity measured at 2.5 T of SmFe11Ti1+xCx (x = 0, 0.5, 0.1, 0.2) alloys heat treated at 850°C for 15 minutes.


![](https://assets.underline.io/uploads/markdown_image/1/image/4b02a146f9f1f24e4dc7ba739af1ff8b.png)

Fig. 2 Microstructures of SmFe11Ti1.2C0.2 sample heat treated at 850°C for 15 minutes. (a)Bright field image using Transmission Electron Microscopy. (b)Dark field image and corresponding EDS mapping image using Scanning Transmission Electron Microscopy. The grains which was shown in dark contrast on the image was region that Ti and C was concentrated.

poster

Experimental methods allowing for the detection of single spins in the solid-state, which were initially developed for quantum information science, open new avenues for the development of highly sensitive quantum sensors [1]. In that context, the electronic spin of a single nitrogen-vacancy (NV) defect in diamond can be used as an atomic-sized magnetometer, providing an unprecedented combination of spatial resolution and magnetic sensitivity under ambient conditions [2]. In this talk, I will illustrate how scanning-NV magnetometry can be used as a powerful tool for exploring condensed-matter physics, focusing on chiral spin textures in antiferromagnetic materials [3-5].

Exploring antiferromagnetic order at the nanoscale with a single spin microscope

Hydrodynamic electron flow, where electrons in a conductor flow collectively - akin to a fluid, is a unique signature of strong electron interactions in a material. This effect has been observed in 2D materials, but observations in bulk materials are intriguing as high-carrier density should screen the interactions. In this talk, I will discuss a recent measurement of hydrodynamic flow in the semimetal WTe2, allowing us to gain insight into the microscopic origin of its electron interactions. We image the spatial profile of the electric current by using a nitrogen-vacancy scanning tip. Using coherent quantum sensing, we obtain magnetic field resolution of ~10nT and spatial resolution of ~100nm. The current pattern we observe differs substantially from the flat profile of a normal metal, and indicates correlated flow through the semimetal. The pattern also shows non-monotonic temperature dependence, with hydrodynamic effects peaking at ~20 K. We compare our results to a model which combines ab initio electron scattering rates and the electronic Boltzmann transport equation. The model shows quantitative agreement with our measurement, allowing us to extract the strength of electron-electron interactions in our material. Furthermore, we conclude that electron interactions are phonon-mediated. This result opens a path for hydrodynamic flow and strong interactions in a variety of new materials.

Imaging hydrodynamic flow in WTe2 with cryogenic quantum magnetometry

The current-induced torque is one of the most important phenomena in spintronics as it provides a way to control magnetic order parameters by electrical means. So far, most studies on the microscopic mechanisms of the current-induced torque have focused on the role of spin current carried by conduction electrons, which exerts spin-transfer torque on the magnetization upon the injection into a ferromagnet. In solids, however, electronic Bloch states originate from the atomic orbitals of the constituent atoms. Thus, while it is natural to expect that such orbital information may be used to control the magnetization because the orbital degree of freedom carries the angular momentum as the spin degree of freedom does, the role of orbitals in the physics of the current-induced torque has been barely investigated. In recent years, we uncovered mechanisms of generating the electronic current carrying finite orbital angular momentum such as the orbital Hall effect (OHE) [1] and proposed to utilize the orbital current for controlling the magnetization [2]. The latter is shortly denoted by “orbital torque” (OT) nowadays. In this talk, I review recent theoretical progress in the mechanisms of the OHE and the OT. In the first part, I will explain that the OHE arises in various metals regardless of their strength of the spin-orbit coupling, whose magnitude is typically an order of magnitude larger than that of the spin Hall effect (SHE) in heavy metals [3]. In fact, the SHE is a concomitant effect of the OHE, whose hierarchical relation will be explained. In the second part, I will discuss the mechanisms of the OT. The main problem is that it is hard to distinguish the orbital contribution and the spin contribution to the torque on the magnetization in most torque measurements. This is one of the main difficulties to quantify the OT. Theoretically, we recently developed a general theoretical formalism that tracks the transfer of the angular momentum in solids between the lattice, the local magnetic moment, and the electron’s spin and orbital, and successfully implemented it within the density functional theory framework [4]. This enables us to understand the microscopic nature of the OT and quantify different competing contributions. Finally, I will also discuss unique qualitative features of the OT mechanisms: significant dependence of the interface orbital transparency on the crystallinity and long-range transport and dephasing in a ferromagnet [5].

Theory of Orbital Hall Effect and Current-Induced Torques by Orbital Current

Circularly polarized light with spin angular momentum is one of the most valuable probes of magnetism. Recently we demonstrated that light beams with orbital angular momentum (OAM), or vortex beams, can also couple to magnetism exhibiting dichroisms in a magnetized medium [1.2]. Terahertz (THz) vortex beams with various combinations of the orbital angular momentum l=±1, ±2, ±3, and ±4 and spin angular momentum s = ±1, or conventional circular polarization, were used for studies of the magnon spectra at the antiferromagnetic resonance conditions in TbFe3(BO3)4 and Ni3TeO6 single crystals. In both materials we observed strong vortex beam dichroism for the magnon doublet, which is split in an external magnetic field applied along the spin ordering direction. The absorption conditions at the magnon frequencies depend on the total angular momentum of light j that is determined by the combination of the spin and orbital angular momenta: j=s+l. For the higher orders of l, the selection rules for AFM resonances dictated by l completely dominate over that for conventional circular polarization. Our results demonstrate the high potential of the vortex beams with OAM as a new spectroscopic probe of magnetism in matter. In addition to the results for AFM materials, we will also present our recent experiments with vortex beam spectroscopy of the Landau level resonances in 2DEG semiconductor heterostructures in high magnetic field. Various parts of this work was performed in collaboration with T. N. Stanislavchuk1, P. Marsik 2, L. Bugnon2, M. Soulier2, C. Bernhard2, V. Kiryukhin3, and S.-W. Cheong3 1 Department of Physics, New Jersey Institute of Technology, Newark, New Jersey 07102, USA 2 Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland 3 Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.

Competition between orbital and spin angular momenta of the THz beams at the antiferromagnetic resonances and Landau level transitions

There exist needs for advanced inductors that are (1) power dense, (2) highly efficient, and (3) high temperature stable for a range of power electronics applications which include on-board converters and off-board charging systems for electric vehicles. Nanocrystalline soft magnetic alloys are of great interest for medium frequency and medium to high power applications due to their large saturation flux density relative to ferrites, as well as their improved losses and reduced magnetostriction relative to amorphous alloys. However, state-of-art commercial Fe-based nanocrystalline alloys display inherently large permeabilities and consequently they require gapping for high power inductor applications and suffer from inherent limitations of mechanical brittleness and relatively poor temperature stability (rated at 150C). Recent advances in Co-based nanocrystalline alloys have enabled a new class of highly scalable inductors which overcome the limitations of existing Fe-based nanocrystalline alloys through in-line tension anneal processing to enable a new level of control for large-scale inductor designs not previously possible without the requirement for core gapping. Local permeability control (i.e. permeability engineering) is made possible through real-time controls of applied tension and controlled thermal processing during the in-line processing step, of particular interest for reduced peak temperature rise and highly power dense inductor designs by engineering the distribution of magnetic flux throughout the core. Advanced thermal processing techniques can also be applied during the in-line processing stage to tailor the characteristic spatial length-scale and distribution of the spatially varied permeability profile, and after the in-line processing to tailor domain structure and optimize losses. Temperature stability of magnetic properties are also far superior to traditional Fe-based alloys, with current experiments showing the potential for stability of structure and magnetic properties as high as 400C and even approaching 500C. The presentation will address the latest advances in Co-based nanocrystalline strain annealed gapless inductors for power dense inductor applications. Topics to be addressed will include: 1) Phase identity and magnetic property variation as a function of chemistry in Co-based nanocrystalline alloys; 2) The latest in tension annealing at scale and spatially tuned permeability engineering methods; 3) Demonstrations of engineered permeabilities as well as optimized domain structures for taliored magnetic properties; 4) Development of tailored multi-objective optimization tools specifically for permeability engineered gapless core inductors; 5) Application of advanced lmulti-objective optimization tools for inductor design and benchmarking in both electric vehicle and medium voltage power electronics applications; The presentation will conclude with recent experimental results as well as emerging ideas and future perspectives for highly optimized thermal processing methods and techniques, including spatial optimization of the crystallization process and consequently the magnetic properties through spatially tailored rapid thermal processing with electromagnetic field-assisted methods and techniques.

Power Dense Inductors Based Upon Co-Based Nanocrystalline Alloys

This presentation will focus on the applications of Soft Magnetic Components and Materials for Emerging Power Conversion Applications such as Solid State Transformer [SST] Technology and several power conversion systems at both Medium-Voltage [MV] and Low-Voltage [LV]. The re-evaluation of conventional magnetics solutions has become important and essential due to the emergence and adoption of WBG [Wide-Band Gap] power devices such as SiC and GaN devices. These devices not only enable co-design of MV and higher switching frequency, but also enable higher temperature operations requiring characterization of magnetics for such specifications. This presentation will cover advances in medium frequency magnetics for WBG devices based power converters and especially for high power converters. It will highlight the latest advances in soft magnetic material qualification and characterization under non-sinusoidal waveforms. It will provide an overview of magnetic core loss models and implications for thermal modeling. It will also address novel techniques for understanding leakage inductance and anomalous losses due to leakage flux. The novel concept of strain annealing for permeability engineering and design opportunities for heterogeneously tuned permeability cores in high power converter applications will be addressed.

Solid State Transformer Technology Based on Advanced Materials and Design Concepts

A review of soft magnetic amorphous and nanocrystalline alloys currently used in the market along their primary industrial applications will be discussed. The distribution transformer market continues to be the largest volume application of Fe-based amorphous foil with higher efficiency standards globally helping to drive the growth of amorphous-based transformers. High permeability grades of amorphous foil have largely supplanted the convention grades due to the higher induction levels (1.63T) and increased stacking factor (&gt;90%). Magnetic domain refinement of amorphous foil, further reducing the core losses, is now commercially available. Amorphous foil has long been envisioned for high efficiency electric motors. The emerging trends with electric vehicles have revitalized the efforts to incorporate amorphous and nanocrystalline foils as the motor lamination materials. There are many approaches to fabricate these motor components and we will discuss the methods that have been industrially adopted. FeCo based amorphous alloys further enhance the induction levels (1.8T) and can be viable in these applications. Nanocrystalline alloys of the FeBSiNbCu composition have now become an industry standard for ultra-low loss, high frequency and high permeability applications. Advanced processing methods have produced higher induction nanocrystalline alloys with higher Fe and lower Nb content. There are also new FeCo and FeNi nanocrystalline alloys being developed specifically suited towards gapless inductor and motor applications that will be discussed.

Recent Advances and Remaining Challenges in Manufacturing of Amorphous and Nanocrystalline Alloys

For the regular machines, the pole-pairs of machine stators and rotors are identical, where the torque is produced by the single working harmonic from the rotor and stator magnetic fields. During the last hundred years, numerous studies have been done to enhance the working harmonics and weaken the non-working harmonics, so as to acquire the sinusoidal air-gap magnetic fields and improve the quality of torque. The presentation will provide a view on electrical machines from the third eye –Flux Modulation point of view. As a new type of machine, the flux modulation PM machines, have drawn more and more attention due to their great torque density capability. Compared with regular PM machines, the pole-pairs of armature windings and rotor PMs in flux modulation machines are different, where the torque is generated by multiple working harmonics of PM magnetic fields and armature magnetic fields. Under the same electric and magnetic loadings, the flux modulation machines can acquire nearly double torque density of regular PM machines. This presentation will introduce flux modulation fundamental operation principles, machine main features, and topologies including multiple magnetomotive force harmonic machines, multiple permeance harmonics machines and double-modulation machines. Applications, challenges, and research opportunities will be discussed as well.

Flux Modulation Machines – Innovation & Beyond

Arguably the pinnacle of motorsport are race cars and therefore an excellent showcase for new technologies from the different areas of automotive systems. Racing “should” utilize components that are beyond the state-of-the-art and within the Advanced Electromagnetics Group (www.ae-grp.nl) we are providing powertrains and test systems for the design, testing, and validation of high-tech and innovative race car powertrains for all-electric racing championships. These e-racing championships are not something that is started in the 21st century. No, already in 1899 Belgian driver and engineer Camille Jenatzy drove flat out in his torpedo-shaped ‘La Jamais Contente’ (‘never satisfied’) in a sparsely populated area to the northwest of Paris and became the first person to reach more than 100 km/h in a car [1]. Even though the electric powertrain failed to dominate the car industry in the twentieth century, 115 years later in 2014, Formula E appeared with its first-ever race in Beijing, China. Founded in 2011, this is an all-electric championship that showcases around the world a combination of sustainability claims, entrepreneurial spirit and commercial savviness. In Formula E all cars are aerodynamically similar but have some technological differences. Formula E was helped by the automotive world entering the ‘Dieselgate’ or ‘Emissionsgate’ in 2015. Despite these achievements, Formula E still struggles to showcase the technology to the public. Manufacturers are accumulating ever more know-how on electric cars, where Formula E may even turn out to be a hindrance in terms of innovative solutions. As such, the rulebook has to keep track of what is in it for the OEMs that participate. As an example, the Porsche Taycan model has a peak charging capacity of 270 kW and is one the fastest electric vehicles currently on the market. However, Formula E 2020 vehicles charge at a peak rate of 100 kW. Some motorsport fans have mocked the city based racetracks, and Formula E cars were nicknamed ‘hairdryers’ for not having the classic racing sound. In the beginning drivers had to change vehicles during the race because of the batteries. Especially discussed was the ‘Fanboost’ (an e-voting service providing your favourite driver with extra power in the race). However, what ever is said it is a racing class that is on the move and aim to adapt new technologies. For example, in the FIA Formula E season 3, the VENTURI team used an inverter with insulated-gate bipolar transistors/ Silicon Carbide Schottky Barrier Diode module. It reported a 2 kg weight reduction and 19% size reduction compared season 2 inverter with IGBT module [2]. In the next season a full Silicon Carbide module was used, where the inverter is capable of operating at 150°C junction temperature with a reduced switching losses of 75% compared to the IGBT solution. This opens the path for integrated motor that will use the high power density of SiC devices, and their high efficiency and cooling loop simplification thanks to the high temperature operation capability of SiC devices [3]. These electrical machines and drives not only have to withstand large forces, but also need to be designed to account for many advanced innovations. High-torque densities are a key requirement in traction machines. Using a multiple air gap design can achieve up to 60 percent higher torque density relative to single airgap machine. This talk will provide an overview of advanced powertrain technologies that aided to progress vehicle racing. By a careful choice and sizing of powertrain components coupled with an optimal energy management strategy from the batteries, attractive racing will be here to stay.

Formula E: Electric Machines and Drives Strategy

Reducing the rate of CO2 emissions for hybrid electric vehicles (HEV) and improving the autonomy for full battery electric vehicle (BEV) constitute major challenges for motor manufacturers. That can be done by losses reduction in each part of the electric powertrains. In the electric motors, using high grades magnetic material and optimal design allows reducing iron losses in the important area of the Torque-Speed plane. That is why segmented stator cores mixing grain oriented electrical steel (GOES) and non-oriented electrical steel (NOES) constitute a serious way of improvement. The goal of the paper is to present the existing structures with, for instance GOES teeth and NOES yoke, and to analyze the contribution of the high grade steel in the automotive motor improvement, in terms of efficiency, masse and volume. GOES has strong advantages in terms of iron losses and flux density at saturation, when it is magnetized in the Rolling Direction (RD). GOES has the drawback of being very anisotropic and the performance is not so interesting in the Transverse Direction, compared to NOES, especially in term of iron losses at high induction and high operational frequencies [1]. That implies to adapt the machine geometry to the specificities of this steel [2] [3] [4]. Another disadvantage of GOES is the sensitivity to the manufacturing processes: bending, cutting, compacting… [3]. From a micro-structural point of view, cutting the sheets causes a destruction of the grains close to the cutting border. At a macroscopic scale, that reduces the magnetic performance, depending not only on the cutting technique but also the dimensions of the sheet [5]. First, in the full paper, the authors present the existing magnetic circuit structures and how the constraints linked to the high anisotropy ratio has been taken into account. The electric motor analyzed mixes GOES teeth and NOES yoke, as shown in Fig.1. Second, the question of the modelling is posed. The full analytic simulation of the motor is not really adapted taking into account the complexity of the anisotropy. The Finite Element software applications integrate now both anisotropy and saturation, but not always in 3D. The strong difficulty is that the magnetic characteristics differ as a function of the magnetization angle. As a result, the results are not enough accurate in term of flux density distribution. The loss models, when they are implemented for GOES, are not reliable when the sheet is magnetized in multiple directions. Third, in order to analyse the contribution of the elements constituting the magnetic circuit, the authors propose a device, shown in Fig. 2, for numerical and experimental tests. It is designed in order to reproduce the phenomena occurring in the electrical motors, especially in the region between the teeth and the yoke. To do that, it combines two Epstein frames modified to magnetize different magnetic structures. The goal is to analyse the flux densities in the magnetic circuit and the iron losses, depending on several parameters as different geometries of junctions between the segments. The angle and the depth of insertion of the teeth into the yoke will be analysed. It allows also to evaluate the effect of the flux passing not directly in a teeth, but only the yoke. That happens in fractional slot permanent magnet machines and, in that case, the TD is fully solicited. Then, the nature and the grades of the materials will be tested with 0,20mm GOES and NOES. Effect of manufacturing will also be shown with experimental test made with cut laminations. Fourth, an existing full NO steel reference motor will be numerically compared with an improved machine made with mixed NOES and GOES. The comparison will be made on local quantities (flux density, etc) as well as on integral quantities (Flux, EMF, Electromagnetic torque and losses). The authors will also present simulation results showing the efficiency improved by the use of GOES.

![](https://assets.underline.io/uploads/markdown_image/1/image/aed73ebd63bf37d4e50d037464f03e5c.jpg)

Fig.1

![](https://assets.underline.io/uploads/markdown_image/1/image/548defbb0b245a7f85b58ec80f02f477.jpg)

Fig. 2

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Exploring antiferromagnetic order at the nanoscale with a single spin microscope

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