LaFe13-x-yMxSiyN3 compounds (M = Mn) were synthesized by flowing ammonia over intermetallic precursors at 623 K for 4 hours. The nitrides were characterized by room temperature powder X-ray diffraction, magnetic thermogravimetry (mTGA), differential scanning calorimetry (DSC), and magnetization measurements. The nitrides derived from Si-poor (y â‰¤ 3) cubic intermetallics retain the NaZn13-type crystal structure and the lattice parameters, a, of the synthesized trinitrides increase by ~3 % compared to the precursors. The nitrogenation increases ferromagnetic ordering temperature by approximately 200 K when compared with the corresponding nitrogen-free NaZn13-type phases, but unlike those of the latter, TCs of the nitrides are independent of the Fe/Si ratio. Partial substitution of Fe with Mn lowers TC of the trinitride similarly to the non-nitrogenated precursors. The magnetic ordering transitions in the nitrides are broad, resulting in rather weak magnetocaloric effects peaking at -2.0 J/Kg K for a 0 to 5 T magnetic field change. The nitrides are stable below 750 K, but they begin to lose nitrogen above this temperature, fully decomposing above 1050 K. Ames Laboratory is operated for the U.S. Department of Energy (DOE) by Iowa State University under Contract No. DE-AC02-07CH11358. This work was supported by the Division of Materials Science and Engineering of the Office of Basic Energy Sciences of the U.S. DOE.

Synthesis and magnetic properties of LaFe13 x

We will present our results on the possibility of deriving high performance magnet powder for bonded magnets production via hydrogen decrepitation (HD) and heat treatment. Applications of permanent magnets (PMs) in the energy conversion industry and in electric vehicles have attracted enormous recent interest. The flexibility of bonded magnets manufacturing allows for high degree of magnet shape customization. They are manufactured by blending rare earth magnet powder with thermoset or thermo-plastic polymers. The magnetic properties of bonded magnets, such as maximum energy product, depend on the loading of the starting powders. By developing an approach for producing bonded magnets via HD, we will enable future opportunity to recycle end-of-life sintered magnets into high performance bonded magnets. 
In this work, HD of N52 sintered magnets were performed at 1bar, 1.5bar, 2bar and 4bar pressure. The resultant powder due to the absorption of the hydrogen gas and pulverization of the material shows soft magnetic characteristics. The HD powder was characterized by DSC to find the degassing temperature. Fig.1 shows the DSC curve of 4 bar pressure produced HD powder. The peak at T1=151°C attribute to removal of H2 from Nd2Fe14B phase, T2=175°C conversion of Nd trihydride to Nd dihydride and the Peak at T3=655°C correspond to formation of Nd rich phase at grain boundary after degassing from NdH2 1. Hence, we carried out degassing in vacuum furnace at 800°C for 2h. The degassed samples show hard magnetic properties (Fig.2) however, final powder product magnetic property does not vary with pressure in HD process. Therefore, we selected the powder treated at 4bar, which shows 30 MGOe maximum energy product for bonded magnets development. The bonded magnets were developed by compression molding of a mixture of 60 vol% of magnetic powder and 30 vol% Nylon 12 at 180 °C for 5 min, followed by ambient cooling. Throughout the process, 3kPa pressure was applied to achieve maximum density. The bonded magnets had a density of 4.1 g/cc. Magnetic field alignment was performed on the bonded magnets at 180 °C under 0.8 T field to obtain 13MGOe maximum energy product. 
**References:** M.Zakotnik, E.Devlin, I.R.Harris, A.J.Williams, Journal of Alloys and Compounds,
450, 525-531, 2008 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/808cb55f27f0aedb207995c564480198.png) 
Fig. 1 DSC of HD powder 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/613d0e1318ab6239d6cca5892fae0e61.png) 
Fig. 2 MH loop of annealed powder

Bonded Magnets Development using Hydrogen Decrepitation

While tetragonal MnAl with the L10-type structure (P4/mmm #123) is metastable, it displays good intrinsic hard magnetic properties such as large magnetization (Ms=110 emu/g), high magnetocrystalline anisotropy field (HA=40 kOe), and moderate Curie temperature (Tc=600 K),1 which make it highly attractive as a sustainable rare-earth free permanent magnet. However, the metastable behavior of the MnAl L10-phase promotes the formation of structural defects that degrade its intrinsic magnetic properties such as the local magnetocrystalline anisotropy (MCA). In this work, we study the effects of a partial replacement of Al by Ga on the stability of the L10-phase, and both the magnetization and the MCA using a first-principles density functional calculation. We find that increasing the Ga content, enhances the phase stability while the total magnetic moment per formula unit (f.u.) remains almost unchanged. The site-, atomic- and spin-resolved MCA has been estimated by evaluating the spin-orbit coupling energy using a second-order perturbation approximation. Structural distortion, chemical effects and different spin components in Mn(Al1-xGax) all contribute to the MCA. The site- and atomic-resolved MCA calculations show that the MCA energy (MAE) mainly comes from the Mn atoms. With increasing Ga content, the MAE at both Mn and Al(Ga) sites increases and the total MAE increases from 0.2 meV/f.u. for x=0 to 0.34 meV/f.u for x=1 (Fig. 1). However, the structural distortion induced by the partial replacement of Al by Ga reduces the MCA. The spin-resolved MCA and band structure calculations indicate that the microscopic origin of high MCA is mainly associated with the spin flipping behavior near the Fermi level, induced by the spin-orbit coupling. The derived effective magnetic anisotropy field increases from 37 kOe (x=0) to 46 kOe (x=1), in agreement with experiments. Doping with Ga improves the stability of the L10 structure and enhances the magnetic anisotropy field, which facilitates the development of high coercivity Mn-Al based permanent magnets. 
**References:** 1 L Pareti, F. Bolzoni, F. Leccabue, A.E. Ermakov, J. Appl. Phys. 59, 3824 (1986) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/2686cbc73adcf807336315c2b6ddbdee.png) 
Fig. 1 Dependence of MAE on Ga content, x, in Mn(Al1-xGax).

Constituent contribution to the magnetocrystalline anisotropy in Mn(Al1 xGax)

Surface Permanent magnet (SPM) motors are generally used in small traction applications due to high power density, simple designing and easy manufacturing processes.
SPM motors dominates the market particularly for small permanent magnet motors.However, the major concern with the SPM motors is their higher demagnetization risks due to close
exposure of PM to the stator windings [1]. In order to avoid demagnetization risks, such motors use the critical rare-earth permanent magnets (REPMs) which are prone to supply disruption
and critical availability, hence poses a long-time sustainability challenge [2]. Many attempts have been made [3-4], for reduction of critical REPMs in permanent magnet motors. However,
most of these attempts focus on the interior permanent magnet motors but rarely on SPM motors.
This work proposes a reduced rare-earth sandwich surface permanent magnet (SSPM) motor, which uses cost-effective and abundant ferrite permanent magnets (FPM, (BH)max=3 MGOe)
between two high-energy product rare-earth PM (Nd-Fe-B, (BH)max =33 MGOe) layers. The main idea of such a magnet structure is that the REPM drives the FPM to operate at higher
flux density which reduces demagnetization susceptibilities of the FPM without degrading torque capability of the motor. Equivalent magnetic circuit (EMC) approach is applied to
investigate the SSPM motor and the approach can also be applied to represent a sandwiched multiple type magnet structure with an equivalent single magnet. The performance of
sandwich-type magnets is carried out on a small traction motor (1.75 kW, 640 rpm motor) [5]. The output torque and demagnetization performance of the motor with different magnets are
given in Table-I and Fig.1. The present work offers a way to reduce the consumption of critical REPM materials in PM motors without significant performance degradation.
This research was supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy,
Advanced Manufacturing Office. 

**References:** 


[1] A. M. El-Refaie. T. M. Jahns, and D. W. Novotny, IEEE Trans. Magn., vol. 21, pp. 34-43, 2006. 
[2] R. T. Nguyen, D. D. Imholte, A. C. Matthews, and W. D. Swank, Waste Management, vol. 83, Pp. 209-217, 2019, 
[3] W. Wu, X. Zhu, L. Quan, Y. Du, Z. Xiang and X. Zhu, IEEE Transactions on Applied Superconductivity, vol. 28, pp. 1-6, 2018. 
[4] Y. Chen, T. Cai, X. Zhu, D. Fan and Q. Wang, IEEE Transactions on Applied Superconductivity, vol. 30, pp. 1-6, 2020. 
[5] N. Y. Braiwish, F. J. Anayi, A. A. Fahmy and E. E. Eldukhri, 49th International Universities Power Engineering Conference (UPEC-2014), pp. 1-5, 2014. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/1385db3e839f65a432798cee8de616c9.png)

Design and Analysis of Reduced Rare Earth Magnet Surface Permanent Magnet Motor using Sandwich Magnets

Recently, more attention has been paid to developing rare earth free permanent magnets. (Fe0.7Co0.3)2B with tetragonal structure shows good intrinsic hard magnetic properties. It has a large saturation magnetization (Js=13 kGs), a high Curie temperature (Tc=940 K), and a moderate uniaxial magneto-crystalline anisotropy (MCA) field (HA= 7.7 kOe) [1-4]. In addition to the good intrinsic properties, the hard magnetic properties such as coercivity are also sensitive to microstructure. In particular, the coercivity reduces sharply upon the existence of the low MCA regions in microstructure, which favors the nucleation of the magnetic domain for the magnetization reversal. There always exist some local structural defects in real magnets, such as chemical composition fluctuation, local strain, and even the second impurity phase. In this work, the sensitivity of MCA to composition fluctuation and structural defects has been studied by a first-principles DFT calculation. The calculated MCA energy (Emca) of (Fe0.7Co0.3)2B with perfect structure is 0.125 meV/f.u. A fluctuation of cobalt content of 10%, or 1% isotropic lattice strain (Fig.1), or 2% tetragonal distortion will cause a reduction of Emca up to 30% in (Fe0.7Co0.3)2B. The spin-resolved MCA analysis indicates that spin-up and spin-down electrons contribute positively to Emca while the spin mixing has a negative contribution (Fig.1). The interplay of these different contributions results in optimized chemical composition or geometrical structure to maximize MCA. Micromagnetic simulation indicates that the coercivity decrease from 2.2 kOe to 1.0 kOe in an isotropic magnet of (Fe0.7Co0.3)2B with an average grain size of 30nm by considering the existence of randomly distributed local reduction of MCA energy up to 30%. This work is supported by the Critical Materials Institute (CMI), an Energy Innovation Hub funded by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. Ames Laboratory is operated for the U.S. DOE by Iowa State University under Contract No. DE-AC02-07CH11358.

![](https://assets.underline.io/uploads/markdown_image/1/image/c11d0f0079ff1d8d06c4d6f00a36a5d9.jpg)

Calculated spin-resolved- and total- magnetocrystalline anisotropy energy as a function of lattice strain in (Fe0.7Co0.3)2B.

Robustness of magneto-crystalline anisotropy and its effect on coercivity in (Fe0.7Co0.3)2B

Nd-Fe-B bonded magnets have been widely applied in data storage and consumer electronic devices [1-3]. Theoretically, the maximum energy product of anisotropic magnets is four times as that of isotropic magnets, hence making anisotropic bonded magnets attractive. To produce bonded magnets, magnetic powders are mixed with thermoset- or thermoplastic- polymers for compression or injection molding methods, respectively. In addition to the specific performance of the magnetic powder used, a higher remanent magnetization, hence high energy product, can be achieved with a higher loading fraction of magnetic powder. For anisotropic bonded magnets, a high degree of magnetic alignment (DOA) of the powders in polymer matrix is important. However, the desire for higher loading fraction needs to be balanced with the requirement for good mechanical properties which decreases with loading fraction. As part of our endeavor to develop high-performance Nd-Fe-B bonded magnets, we studied different processing parameters that contribute to the resultant magnetic alignment and hence magnetic properties of anisotropic Nd-Fe-B bonded magnets. We select Nylon12 as binder and Magfine Nd-Fe-B powder to fabricate bonded magnets. Magfine powder is a commercial Nd-Fe-B anisotropic magnetic powder produced by hydrogenation, disproportionation, desorption, and recombination (HDDR). Different loading fractions of Nd-Fe-B powder were mixed with binder and warm-compacted (450 K) into bonded magnets with a diameter of 8mm and a length of 5mm. To magnetically align Nd-Fe-B powder in the as-prepared bonded magnets, a post-compaction magnetic field alignment was performed with an applied external magnetic field of up to 30 kOe. Samples were heated in magnetic fields from 300 to 530 K (Nylon-12) with a dwell time of 15 min at 530 K, and then cooled down to 300 K. After each alignment process, the magnetic hysteresis loops were measured again at 300 K using a Quantum Design Versalab VSM magnetometer. For Nd-Fe-B bonded magnet with 70% loading fraction of magnetic powder, the magnetic remanence increases from 4.8 kGs to 7.2 kGs, while the intrinsic coercivity remains almost unchanged (12 kOe) upon magnetic alignment (Fig. 1). The enhancement of remanence is due to the magnetic alignment of magnetic powder in bonded magnets. Thermomagnetic measurement data shown in Fig. 2 reveal a jump of magnetization at 480-490 K during post-compaction annealing under external applied fields. This temperature is slightly higher than the melting point of Nylon-12 (450 K), which means the binder (Nylon-12) is melted and at a low viscous state. The low viscosity of binder reduces friction between binder and particle and facilitates the magnetic powder alignment under magnetic field. This is a necessary condition for achieving alignment of magnetic particles in Nd-Fe-B bonded magnets during post-compaction magnetic alignment process. We performed magneto-static calculations which show that the DOA are determined mainly by the interplay between the Zeeman energy (Eapp.) and the inter-particle magnetic-static energy (Estat.) at the chosen alignment temperature and the applied magnetic fields. The good alignment can be achieved by an alignment magnetic field which is twice as its coercivity in anisotropic Nd-Fe-B bonded magnet.

**References:**

1. J. M. D. Coey and K. O’Donnell, J. Appl. Phys., vol. 81, no. 8 PART 2B, pp. 4810–4815, 1997. 2. J. Ormerod and S. Constantinides, J. Appl. Phys., vol. 81, no. 8 PART 2B, pp. 4818–4820, 1997. 3. M. P. Paranthaman et al., Jom, vol. 68, no. 7, pp. 1978–1982, 2016.

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/aa6cc50624b84ea940e8b8226900b19a.jpg)
Fig. 1. Magnetic hysteresis of J-H of nonaligned- and aligned samples for 75 vol% Magfine Nd-Fe-B Nylon bonded magnets.

![](https://assets.underline.io/uploads/markdown_image/1/image/a31262fd5b839b2fb205f3d5100df188.jpg)
Fig. 2. Thermomagnetic curve of J-T for 75 vol% Magfine Nd-Fe-B Nylon bonded magnets

 Magnetic alignment in anisotropic Nd-Fe-B bonded magnets

NOB: Magnetocaloric Materials I

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Presentations

Synthesis and magnetic properties of LaFe13 x

Bonded Magnets Development using Hydrogen Decrepitation

Constituent contribution to the magnetocrystalline anisotropy in Mn(Al1 xGax)

Design and Analysis of Reduced Rare Earth Magnet Surface Permanent Magnet Motor using Sandwich Magnets

Robustness of magneto-crystalline anisotropy and its effect on coercivity in (Fe0.7Co0.3)2B

Magnetic alignment in anisotropic Nd-Fe-B bonded magnets

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