United States

We have fabricated isotropic Pr-Fe-B thick-film magnets with the thickness of 0.25 mm on a stainless shaft using a PLD (Pulsed Laser Deposition) method and applied them to an ultra-stepping motors with the diameter of less than 3 mm by taking advantage of Pr2Fe14B phase with a large anisotropic magnetic field at room temperature [1]. In this study, we focused on the fact that the linear expansion coefficient of Nd element (9.6×10-6 1/K ) is closer to that of stainless steel(10～11×10-6 1/K) than that of Pr element( 6.7×10-6 1/K ). Moreover, evaluation on the temperature dependence of magnetic properties and observation in the mechanical characteristic of Nd-Fe-B thick-film magnets on a stainless substrate (shaft) were carried out.&lt;br&gt;
Figure 1 shows the temperature dependence of the energy product at the operating point of (Nd or Pr)-Fe-B thick-film magnets fabricated on stainless substrates. At 125 °C, the energy product of a Nd-Fe-B thick-film exceeds those of a Pr-Fe-B one and a Nd-Fe-B bond magnet. The result is considered to be attributed to the different temperature dependence of each anisotropic magnetic field for Pr2Fe14B and Nd2Fe14B phases. We also observed the mechanical characteristic of the both films on a stainless substrate and shaft. Several as-deposited Pr-Fe-B film magnets with the Pr contents exceeding 15 at % on the substrate showed exfoliation phenomenon. On the other hand, as-deposited and annealed Nd-Fe-B films (Nd contents : 14 ～ 18 at. %) on the substrate didn’t show mechanical destruction. Although almost all the films showed good adhesion on the stainless shafts as displayed in Fig. 2, one Pr-Fe-B thick-film magnet had a slight crack at the boundary of the shaft and the film. Consequently, enhancement in coercivity of Nd-Fe-B thick-film using an additive at room temperature is a promising method to propose an alternative material of a previously reported Pr-Fe-B thick-film.&lt;br&gt;
**References:**&lt;br&gt;[1] M. Nakano et.al., IEEE Trans. Magn. Vol. 56, 7516303(2020).&lt;br&gt;

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/12a99c2023d5eae1a86663002d5f32c2.png)&lt;br&gt;
Fig 1 Energy product (Pc =1.0) of (Nd or Pr)-Fe-B thick film magnets as a function of operating temperature.&lt;br&gt;
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/24daf7821456da0e79c5dbe705fb128b.png)&lt;br&gt;
Fig. 2 Exfoliation phenomenon of as-deposited (Nd or Pr)-Fe-B thick-films on stainless shafts.&lt;br&gt;

MMM 2022

Development of rare earth thick

We have fabricated isotropic Pr-Fe-B thick-film magnets with the thickness of 0.25 mm on a stainless shaft using a PLD (Pulsed Laser Deposition) method and applied them to an ultra-stepping motors with the diameter of less than 3 mm by taking advantage of Pr2Fe14B phase with a large anisotropic magnetic field at room temperature [1]. In this study, we focused on the fact that the linear expansion coefficient of Nd element (9.6×10-6 1/K ) is closer to that of stainless steel(10～11×10-6 1/K) than that of Pr element( 6.7×10-6 1/K ). Moreover, evaluation on the temperature dependence of magnetic properties and observation in the mechanical characteristic of Nd-Fe-B thick-film magnets on a stainless substrate (shaft) were carried out. 
Figure 1 shows the temperature dependence of the energy product at the operating point of (Nd or Pr)-Fe-B thick-film magnets fabricated on stainless substrates. At 125 °C, the energy product of a Nd-Fe-B thick-film exceeds those of a Pr-Fe-B one and a Nd-Fe-B bond magnet. The result is considered to be attributed to the different temperature dependence of each anisotropic magnetic field for Pr2Fe14B and Nd2Fe14B phases. We also observed the mechanical characteristic of the both films on a stainless substrate and shaft. Several as-deposited Pr-Fe-B film magnets with the Pr contents exceeding 15 at % on the substrate showed exfoliation phenomenon. On the other hand, as-deposited and annealed Nd-Fe-B films (Nd contents : 14 ～ 18 at. %) on the substrate didn’t show mechanical destruction. Although almost all the films showed good adhesion on the stainless shafts as displayed in Fig. 2, one Pr-Fe-B thick-film magnet had a slight crack at the boundary of the shaft and the film. Consequently, enhancement in coercivity of Nd-Fe-B thick-film using an additive at room temperature is a promising method to propose an alternative material of a previously reported Pr-Fe-B thick-film. 
**References:** [1] M. Nakano et.al., IEEE Trans. Magn. Vol. 56, 7516303(2020). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/12a99c2023d5eae1a86663002d5f32c2.png) 
Fig 1 Energy product (Pc =1.0) of (Nd or Pr)-Fe-B thick film magnets as a function of operating temperature. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/24daf7821456da0e79c5dbe705fb128b.png) 
Fig. 2 Exfoliation phenomenon of as-deposited (Nd or Pr)-Fe-B thick-films on stainless shafts.

poster

#### Welcome to the 67th Annual Conference on Magnetism and Magnetic Materials, MMM 2022!

The Conference was held from October 31 to November 4 and offers both in-person and on-demand content.

MMM 2022 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 tutorial, and several special sessions. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

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For high performance and high efficiency, rare earth magnets have been widely used in recent motors. Rare earth is very unstable as a future industry due to limited resources and monopoly of some countries. For this reason, as the price of rare earth magnets and overall materials has increased recently, the issues of cost reduction and weight reduction are increasing. In this paper, iron usage and weight were reduced by changing the existing EPS motor to the STM model [1]. However, the STM model showed low performance compared to the amount of magnet used because large leakage occurred in the lips. To compensate for these shortcomings and to reduce the amount of magnet used, consequent poles were applied. When Consequent pole is applied, the usage of rare earth magnet is greatly reduced. Therefore, the weight and price are greatly reduced. In general, the consequent pole reduces the use of magnets by half, so the performance is also reduced by half. However, in the STM model, the magnetic flux leakage from the lips is greatly reduced by removing the poles. Therefore, the performance is reduced by about 35%, not by half. Therefore, even though the use of magnets has been reduced by half, by applying STM as a consequent pole rather than a general consequent pole with the same performance, many advantages such as weight reduction and reduced use of magnets can be brought. The application of this motor is EPS. For EPS, cogging torque is the most important performance factor. However, when the Consequent pole is applied, only the N pole or the S pole exists and the rest is made of iron, so a lot of cogging torque and torque ripple occurs. In this paper, after applying the consequent pole to the STM model, various methods are applied to reduce the cogging torque. Finally, it can be seen that the weight and magnet usage are reduced with the same performance, and the cogging torque is similarly generated. 
**References:** [1] S. -W. Song, I. -J. Yang, S. -H. Lee, D. -H. Kim, K. S. Kim and W. -H. Kim, "A Study on New High-Speed Motor That Has Stator Decreased in Weight and Coreloss," in IEEE Transactions on Magnetics, vol. 57, no. 2, pp. 1-5, Feb. 2021, Art no. 8201105, doi: 10.1109/TMAG.2020.3012482. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/0abfd8dfb908f1e8bb0f63c25f68ac61.png) 
Fig. 1 Consequent pole applied to STM structure 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/fed13d62fa9eecb87a4406d56e74f4dd.png) 
Fig. 2 STM structure magnetic flux line

A study on the application of consequent poles to the STM model to reduce weight and use of magnets

The use of Nd-Fe-B magnets with Nd2Fe14B, which are used in high performance motors, is increasing. However, it is predicted that inexpensive Nd will become unavailable in near future, and there is a need to reduce the amount of Nd used and develop new magnets [1]. Exchange-coupled nanocomposite magnets consisting of magnetic hard and soft nanoparticles, NPs have been proposed as candidate [2]. The Sm(Fe0.8Co0.2)12 with ThMn12 structure has higher saturation magnetization, Ms, and uniaxial magnetocrystalline anisotropy, Ku than Nd2Fe14B and is expected to be a magnetic hard phase in the Fe-based system without Nd [3]. We investigate the effect of the direction of the α-Fe coating surface and the volume fraction of α-Fe, VFe on the demagnetization process and the maximum energy product, (BH)max of exchange-coupled Sm(Fe0.8Co0.2)12 /α-Fe nanocomposite NPs using LLG simulations [4]. Sm(Fe0.8Co0.2)12 NPs is as reference model #1. The nanocomposite NPs of Sm(Fe0.8Co0.2)12 coated with α-Fe on top/bottom, and both sides are model #2 and #3. For both # 2 and #3, α-Fe layer thickness is 1 nm ≤ tFe ≤ 7 nm. The size of NPs are x = y = 50 nm and z = 100 nm. The magnetic properties of Sm(Fe0.8Co0.2)12 and α-Fe were taken from references [3, 5-7]. The cell volume is 1 nm3. External field, Hex is applied parallel to c-axis of Sm(Fe0.8Co0.2)12 along to z-axis of NPs. Fig. 1 shows VFe dependence of (BH)max for #2 and #3. The (BH)max of #1 was 630 kJ/m3 , while the (BH)max of #2 and #3 with optimized tFe were larger, 636 kJ/m3 for #2 with VFe = 4 % (tFe = 2 nm) and 657 kJ/m3 for #3 with VFe = 12 % (tFe = 3 nm). Fig. 2 shows distribution of demagnetizing field, Hd at Hex = 0 T for #2 and #3. The Hd acting on top/bottom surfaces of NPs was larger for #2, which was coated on top/bottom surfaces with α-Fe, which is larger than Ms of Sm(Fe0.8Co0.2)12, than for #3, which was coated on sides with α-Fe. Therefore, remanence and (BH)max of #3 are larger than those of #2. From the above discussion, it is clear that side coating of magnetic soft phase is effective in increasing (BH)max of Sm(FeCo)12/α-Fe NPs. 
**References:** [1] S. Hirosawa, M. Nishino and S. Miyashita, Adv. Nat. Sci: Nanosci. Nanotechnol., 8, (2017) 013002. 
[2] R. Skomski and J. M. D. Coey, Phys. Rev. B, 48, (1993) 15812. 
[3] Y. Hirayama et al., Scripta Mater., 138, (2017) 62–65. 
[4] M. J. Donahue and D. G. Porter, “OOMMF User’s Guide, Version 1.0,” NISTIR 6376, National Institute of Standards and Technology, Gaithersburg, MD (Sept 1999). ; M. J. Donahue, D. G. Porter (2021), "OOMMF: Object Oriented MicroMagnetic Framework," https://nanohub.org/resources/oommf. (DOI: 10.21981/8RRA-5656). 
[5] Felix Jimenez-Villacorta and Laura H. Lewis, Chapter 7 "Advanced Permanent Magnetic Materials" Nanomagnetism, edited by J. Gonzalez (OCP Publishing Group) (2014). 
[6] D. Ogawa, T. Yoshioka et al., J. Magn. Magn. Mater., 497, (2020) 165965. 
[7] T. Fukazawa, H. Akai et al., J. Magn. Magn. Mater., 469, (2019) 296-301. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/3a61bed85d0536499bdd51d5c215ec21.png) 
Fig. 1 VFe dependence of (BH)max for #2 and #3. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/a2b7eb05cc1ea092f5b586fe81fd43cf.png) 
Fig. 2 Hd distribution on the top surface and the cross-section of NPs for #2 and #3 at Hex = 0 T.

Maximum Energy Product of Exchange coupled Sm(FeCo)12/α

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)

Effects of La3+ and Li1+ co-substitution on structural and magnetic properties of M-type strontium hexaferrite have been studied by using crystallographic and magnetic measurements. Stoichiometric Sr1-xLaxFe12-x/2Lix/2O19 (x=0, 0.25, 0.4, 0.5, and 0.6) samples have been prepared by the conventional ceramic method using La2O3, SrCO3, Fe2O3, and Li2CO3 powders with repeated sinterings at 1250 °C for 24 hours.
XRD patterns showed that when x > 0.6, LaFeO3, SrFeO3-δ, and other spinel ferrite coexisted along with the M-type hexaferrite. Lattice parameters deduced from the GSAS refinement shows that both a and c decrease with increasing x, but the change in c is more outstanding (Table 1). Variations of the saturation magnetization Ms and the coercivity Hc with x was obtained from room temperature VSM measurement as in Table 1. Whereas the Ms decreases slightly with x, the Hc increases with the La3+ - Li1+ co-substitution throughout the doping range examined. Effective magnetic anisotropy constants K are calculated as well from the hysteresis curves using the law of approach to saturation method. K shows slight decrease with increasing x as listed in Table 1. 
XPS scan shows the Li 1s peak at ~56 eV (Fig. 1(a)). Apparently, monovalent Li1+ is non-magnetic. In view of the facts that Li1+ in the lithium ferrite (LiFe5O8) preferentially occupies the octahedral site and that the M-type hexaferrite has the spinel S-block in its structure, the decreasing trend of Ms with x strongly suggests that Li+1 ions preferentially replace Fe3+ ions either at 12k or 2a sites (rather than the 4f2 site in R-block). Non-magnetic substitution at those sites is known to give rise to negative contribution to Ms. Finally, Mössbauer spectra show gradual decrease in 2a intensity, in support of the octahedral 2a site preference of Li1+ in M-type hexaferrite (Fig. 1(b)). 
**References:** 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/df4dab457afcb7e5118c6d0fedb9652a.png) 
Table 1. Various structural and magnetic parameters for Sr1-xLaxFe12-x/2Lix/2O19 (x=0, 0.25, 0.4, 0.5, and 0.6) 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/05367f421b43d801d81539c55a4d55eb.png) 
Figure 1. (a) A comparison of Li 1s XPS scan for Sr1-xLaxFe12-x/2Lix/2O19 (x=0.25 and 0.5) and (b) 57Fe Mössbauer spectrum for Sr0.4La0.6Fe11.7Li0.3O19 taken at room temperature.

Structural and magnetic characterizations of La3+ and Li1+ co substituted M

The magnetization of Mn4C with face centered cubic structure increases with the increase of temperature within a certain temperature range, which means that Mn4C may be applied to the field requiring high working temperature of magnetic materials through further research and development. Unfortunately, Mn4C is a metastable phase [1-3], so it is difficult to synthesize high-purity Mn4C. 
High-purity Mn4C powders was prepared by melt spinning, grinding and magnetic separation in this paper. It is found that high cooling rate is beneficial to obtain high-purity Mn4C material. Moreover, compared with argon gas as the grinding medium, grinding Mn4C melt-spun strips in alcohol solution is not only conducive to refining the size of the ground particles, but also conducive to improving the dispersion of the particles. Therefore, Mn4C powders with higher purity can be obtained after magnetic separation (see Fig. 1).
The magnetization of Mn4C powders remained unchanged with the increase of temperature in the range of 2 K -50 K, but increased with the increase of temperature in the range of 50 K to 300 K (see Fig. 2). This may be because there is a spin glass state in Mn4C powders. At low temperature, the spins are frozen, but the frozen spins are gradually thawed with the increase of temperature. Further investigation is in progress. 
Crystal and magnetic structure of Mn4C powders was investigated by variable temperature neutron diffraction technique. The magnetization change of Mn4C with temperature should be mainly due to its own magnetic phase transition, and is closely related to the antiparallel arrangement of the magnetic moments of Mn atoms at the symmetrical crystal positions 1a and 3c in the Mn4C lattice. The total magnetic moment of crystal cells increases with the increase of temperature. 
**References:** 1. Si, PZ, Qian, HD, Ge, HL,et al. Applied physics letters, 2018, 112(19):192407. 
2.Park ,J, Qian, HD, Si, PZ, et al. Journal of magnetism and magnetic materials, 2021, 527:167765. 
3. Tagawa, Y and Motizuki, K. Journal of physics-condensed matter, 1991, 3(12): 1753-1761 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/65df04ba198f154c12183b9b3f6c217e.png) 
Fig.1 XRD patterns of Mn4C obtained by (a) arc melting, (b) Suction casting, (c) melt spinning technology (50m/s),and (d) grinding and magnetic separation of the same strips as (c) in alcohol solution. (a) (b) and (c) are both heat treated and ground and magnetically separated in argon. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/e3091542db36f8e069365c557c6f6f8e.png) 
Fig.2 (a) Variation of magnetization of Mn4C powder with temperature under different magnetic field; (b) Hysteresis loops of Mn4C powders at 2K-300K

Study on preparation, structure and magnetic properties of high purity Mn4C

Structural changes and evolution taking place in ferrites with increasing processing temperature are crucial from their performance point of view. Three M-type hexaferrites were prepared using solid-state reaction at 650-1250 °C: SrFe12O19 (SrM), BaFe12O19 (BaM), and CaFe12O19 (CaM). The evolution of phases was studied with X-ray powder diffraction and thermogravimetry investigation. The structural studies reveal that the formation M-type phase begins at 820, 850, and 1200 °C, respectively, and different mid-phases of SrFe3-x, BaFe2O4, and CaFe2O4 were formed. The structural studies in all cases were successfully refined using the P63/mmc (No.194) space group but Ca2+ shrank the hexaferrite crystal lattice. Their magnetic properties were studied with respect to their composition and microstructure by scanning electron microscopy (SEM). The different phase evolution leading to the different magnetic properties of M-type hexaferrite were discussed in the present work. 
**References:** 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/36c0fa25d7625bed31a1e2e1bc6aa2e9.png) 
Table 1 The phase evolution with the temperature of SrM, BaM and CaM

Understanding of the Phase Evolution with Temperature in Pure SrM, BaM and CaM

Permanent magnets are an essential material in many electrification technologies, such as electric vehicles and Air mobility. So, Many efforts have paid for enhanced magnetic flux density and robust high temperature for electrification technologies application.
As a representative example, efforts are being made to reduce the negative temperature coefficient coercive force and use less rare earth by developing NdFeB magnet.
Among the rare-earth-free magnets candidates, MnBi alloy have been regarded as one of the most attractive candidates with promising magnetic properties and the positive temperature coefficient coercivity . The theoretical (BH)max value at room temperature of the LTP MnBi is about 17 MGOe and can reach a high real value of 6.5 MGOe at 400 K . This magnetic performance of the LTP MnBi is can be replace NdFeB magnets in high-temperature magnet applications. 
This study has been developed based on Density functional theory(DFT) calculation and experimental. First, thermodynamic calculations were used for MnBi lattice modeling to select substitutable elements for Mn and Bi lattice sites, and then DFT calculations were used to predict magnetic moments. The MnBi-X alloy candidate material selected through prediction was manufactured using the melt spinning method. A vibratory sample magnetometer (VSM) was used to evaluate the magnetic properties and a trial and error method was used to finally optimize the MnBi alloy composition.
MnBi-Sb magnetic powder has a comparative advantage over ferrite magnets and has the same performance as rare earth bonded magnets. (magnetic flux density 4kG, coercive force 9kOe and coercive force coefficient 0.68~0.91%/K) 
**References:** 1. Yang-Ki Hong, AIP Advances., 3, 052137 (2013) 
2. S. Kavita, Journal of Magnetism and Magnetic Materials., Vol. 377, P. 485(2014) 
3. C. Curcio,Physics Procedia., Vol. 75, P. 1230 (2015) 
4. Sumin Kim, Journal of Alloys and Compounds., vol 708, p1245 (2017) 
5. A.M. Gabay, Journal of Alloys and Compounds., vol. 792, p.77 (2019) 
6. Truong Xuan Nguyen, Physica B., vol. 552, p.190, (2018) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/051728167f485b8fd0af85cfee9ba719.png) 
Fig. 1 X-Ray Diffraction (XRD) data of the Mn-Bi-Sb alloys. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/5eb252ebecb83a90c3e1dc96146b4583.png) 
Fig. 2 Analysis of M-H curve in Mn-Bi-Sb alloys.

Development of Mn based Permanent Magnet Material for Electric Motor

Magnetic dead layers (MDLs) can be formed at the interface of ferromagnetic (FM) and non-magnetic thin films as a result of interfacial diffusion typically during the fabrication process [1][2], causing degradation of magnetic layers’ properties, such as the magnetic moment and exchange coupling. For patterned films it also poses thermal stability problems due to a decrease in the magnetic anisotropy energy, leading to a reduction in thermal activation energies [3]. 

X-Ray reflectometry (XRR) has been used in conjunction with polarised neutron reflectometry (PNR) to investigate the formation of magnetic dead layers in Co70Fe30 thin films with Ta interfaces in addition to sample degradation over time. The rate at which the Ta diffuses into the Co70Fe30 layer differs between the top and bottom interfaces resulting in MDLs of different thicknesses, 3.04Å and 1.87Å respectively as indicated in figure 1(b). It is clear that the formation of magnetic dead layers has resulted in a loss of magnetisation in the thin Co70Fe30 layer. 

This is of particular technological importance for spintronic devices in which the magnetic properties at the interfaces are crucial. Ta has been known to provide very good adhesion between the substrate and the soft FM layer. It is also widely used as a passivation layer to prevent oxidisation in air [4]. Our results show that this is not the case, with Ta unsuitable as a seed due to the formation of MDLs and not viable as a capping layer due to oxygen passivation over time as shown by XRR in figure 2. 
**References:** [1] T. L. Monchesky and J. Unguris, Phys. Rev. B 74, 24130 (2006). 

[2] K. Oguz et al., J. Appl. Phys. 103, 07B526 (2008). 

[3] M. Tokaç et al., AIP Advances 7, 115022 (2017). 

[4] H. S. Jung et al., J. Appl. Phys., Vol. 93, No. 10, (2003). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/4fa86217a7c805ccc7036f26a1a59ed3.png) 
Fig. 1. (a) PNR measurements, raw data shown as points while the fitted simulated data is indicated by a solid line. (b) Depth profiles of nuclear and magnetic scattering length density (SLD) for the sample structure in the schematic above. MDLs have been introduced in the interfaces between the top and bottom interfaces of the CoFe layer. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/072c7007a6575d080bf1a6ca3cc9fc39.png)
 
Fig. 2. XRR curves for the sample structure denoted in the inset above. Sample A was measured as soon as deposited whilst sample B was measured 15 months later which has clearly degraded over time as seen on the fringes and as well as the differences in thickness of the sample.

Interface Degradation in Magnetic Multilayer Stacks Characterised by X Ray Reflectometry and Polarised Neutron Reflectometry

Rare earth/transition metal permanent magnets have gained significant interest due to their outstanding performance, which has made them key materials for many applications. The most well-known compounds Nd2Fe14B, SmCo5, and Sm2Co17 combine a large energy density, high Curie temperature, and a large magnetocrystalline anisotropy (MCA). Besides, SmCo5 exhibits the highest known uniaxial MCA1. Due to their importance, a detailed understanding of their hysteresis behavior has come into the focus of research2.
Since the extrinsic magnetic properties of magnetic materials depend on their complex defect and nanostructure, we follow the strategy to disentangle intrinsic and extrinsic properties as well as the effect of specific defects by investigating SmCo5 and Sm2Co17 phases in thin film model systems grown by molecular beam epitaxy (MBE). 
The Sm-Co system, when grown as thin films in a certain parameter range, undergoes a phase decomposition into a nanocomposite of SmCo5 and Sm2Co17 phases. Due to the structural similarity of the two phases, it is challenging to discriminate their phase contributions. Extended X-ray absorption fine structure (EXAFS) analysis combined with transmission electron microscopy (TEM) allows the unambiguous quantification of the nano-domain phase decomposition in the thin films3. 
In this work, we have studied the behavior of the magnetic anisotropy of Co and Sm using - for the first time, to our knowledge - angle-dependent X-ray magnetic circular dichroism (XMCD) at Sm M4,5 and Co L2,3 edges in 1.9 Tesla external applied field. SmCo5 and Sm2Co17 thin films have been grown onto Al2O3 substrates and pre-characterized by X-ray diffraction (XRD) and superconducting quantum interface device (SQUID). XMCD and X-ray absorption spectroscopy (XAS) gave access to element-specific information and have been complemented by detailed atomistic spin dynamics (ASD) calculations. 
Element-specific hysteresis curves demonstrate strong coupling between Sm and Co, however, the spectroscopy indicates different saturation behavior. The XMCD spectra for the Sm M4,5 edges show surprisingly only a minor angle dependence. Using ASD simulations, we estimate the exchange field at the Sm site to be of the order of -200 T. 
**References:** [1] K. J. Strnat & R. M. W. Strnat, J. Magn. Magn. Mater. 100, 36 (1991). 
[2] O. Gutfleisch et al., Adv. Mater. 23, 821 (2011). 
[3] S. Sharma et al., ACS Appl. Mater. Interfaces 13, 32415 (2021).

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