United States

With the development of the 5G applications, micrometer and millimeter microwaves have been full filling the space around people. They not only interfere with tons of electronic devices but damage human health as well. To combat these problems, there is an urgent need for microwave absorption materials. However, most of the research on microwave absorption materials stays within the 2~18GHz frequency range, while the 5G millimeter microwave’s frequency can reach up to 24GHz or higher. Thus, more studies of microwave absorption properties in a higher frequency band are necessary. In this work, we report the microwave absorption properties of several soft magnetic composites in frequency up to 40GHz. Common materials such as iron, Y2Fe16Si, Ce2Fe17N3-δ, La2Fe4Co10B micron powders which experience excellent microwave absorption properties in 2~18GHz are included. Within 2~40GHz, the reflection loss(RL) of iron/paraffin, Y2Fe16Si/paraffin, Ce2Fe17N3-δ/paraffin and La2Fe4Co10B /paraffin composites could reach -46.2dB, -71.4dB, -49.1dB, and -49.0dB, respectively. And their effective absorption bandwidth(RL&lt;-10dB) could reach 16.9GHz, 8.53GHz, 10.08GHz, and 7.4GHz, respectively. Though the measurements are extended to 40GHz, the RL of most of these materials could not maintain a low level at 40GHz, which is restricted by the cutoff frequencies of the materials. The measured data shows that these soft magnetic composites are good candidates for high-frequency microwave absorption materials, while exploring magnetic materials with further higher cutoff frequencies may result in a better performance.&lt;br&gt;
**References:**&lt;br&gt;Hu, Q. W., Qiao, G. Y., Yang, W. Y. et al., J. Phys. D: Appl. Phys., Vol. 53, p.115001 (2020)&lt;br&gt;
Qiao, G. Y., Yang, W. Y., Lai, Y. F. et al., Mater. Res. Express., Vol. 6, p.016103 (2019)&lt;br&gt;
Zuo, W. L., Qiao, L., Chi, X. et al., J. Alloys Compd., Vol. 509, p.6359-6363 (2011)&lt;br&gt;

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/f708b4db425d125194f5d0dce657f7a5.png)&lt;br&gt;
Fig.1 The RL curves with the broadest effective absorption bandwidth of different composites.&lt;br&gt;
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/b7d05a0b606f27825ea5543beca16e60.png)&lt;br&gt;
Fig.2 The RL curves with the minimum RL of different composites.&lt;br&gt;


MMM 2022

The microwave absorption properties of several soft magnetic materials in frequency up to 40GHz

With the development of the 5G applications, micrometer and millimeter microwaves have been full filling the space around people. They not only interfere with tons of electronic devices but damage human health as well. To combat these problems, there is an urgent need for microwave absorption materials. However, most of the research on microwave absorption materials stays within the 2~18GHz frequency range, while the 5G millimeter microwave’s frequency can reach up to 24GHz or higher. Thus, more studies of microwave absorption properties in a higher frequency band are necessary. In this work, we report the microwave absorption properties of several soft magnetic composites in frequency up to 40GHz. Common materials such as iron, Y2Fe16Si, Ce2Fe17N3-δ, La2Fe4Co10B micron powders which experience excellent microwave absorption properties in 2~18GHz are included. Within 2~40GHz, the reflection loss(RL) of iron/paraffin, Y2Fe16Si/paraffin, Ce2Fe17N3-δ/paraffin and La2Fe4Co10B /paraffin composites could reach -46.2dB, -71.4dB, -49.1dB, and -49.0dB, respectively. And their effective absorption bandwidth(RL<-10dB) could reach 16.9GHz, 8.53GHz, 10.08GHz, and 7.4GHz, respectively. Though the measurements are extended to 40GHz, the RL of most of these materials could not maintain a low level at 40GHz, which is restricted by the cutoff frequencies of the materials. The measured data shows that these soft magnetic composites are good candidates for high-frequency microwave absorption materials, while exploring magnetic materials with further higher cutoff frequencies may result in a better performance. 
**References:** Hu, Q. W., Qiao, G. Y., Yang, W. Y. et al., J. Phys. D: Appl. Phys., Vol. 53, p.115001 (2020) 
Qiao, G. Y., Yang, W. Y., Lai, Y. F. et al., Mater. Res. Express., Vol. 6, p.016103 (2019) 
Zuo, W. L., Qiao, L., Chi, X. et al., J. Alloys Compd., Vol. 509, p.6359-6363 (2011) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/f708b4db425d125194f5d0dce657f7a5.png) 
Fig.1 The RL curves with the broadest effective absorption bandwidth of different composites. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/b7d05a0b606f27825ea5543beca16e60.png) 
Fig.2 The RL curves with the minimum RL of different composites.

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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Motor-driven systems are estimated to use over 40% of all global electricity consumption, giving rise to over 6 Gt of CO2 emissions [1]. To reduce the impact, motors should have higher efficiency. Electrical steels, Fe-Si which have low iron losses are commonly used as soft magnetic materials for motors but higher Bs materials have been desired for higher power density motors. It is well known that Fe-Co alloys have the highest Bs among bulk, stable materials. In fact, Permendur, 49Fe-49Co-2V (mass %) is already used in some high-performance motors, since it has a good soft magnetic properties. However, the drawbacks of Permendur are poor workability owing to the existence of a the brittle B2 phase (ordered phase) . In this study, we first conducted neutron diffraction measurements on the Fe-Co alloys with different Co contents to check the existence of the B2 phase in these alloys. And then, the effect of Si/Al addition on magnetic properties of 82Fe-18Co alloy was investigated in order to improve the soft magnetic properties.

Experimental Procedures 
Four samples with different Co contents (49Fe-49Co-2V, 73Fe-27Co, 82Fe-18Co, and 95Fe-5Co) were prepared through melting, casting, forging and annealing processes. The neutron diffraction study was conducted with iMATERIA spectrometer at the Materials and Life Sciences Facility at the J-PARC (Japan Proton Accelerator Research Complex). For the study of Si/Al addition, 0.2 mm-thick sheets with the addition of Si/Al in the range of 0~1.75 mass% were prepared by melting, casting process, followed by forging, annealing, hot and cold rolling processes. Magnetic properties were measured with a BH-tracer.

Results 
The result showed that 49Fe-49Co-2V and 73Fe-27Co alloys contained the B2 phase. On the other hand, 82Fe-18Co and the 95Fe-5Co did not contain B2, which suggests that these two alloys will likely to have good workability. Therefore, we chose 82Fe-18Co alloy for the investigation of Si/Al addition. Fig. 1 shows the soft magnetic properties of 82Fe-18Co with and without Si/Al addition. It was found that the small addition of Si/Al reduced the iron loss while maintaining high Bs. 
**References:** [1] Paul Waide & Conrad U. Brunner et al., IEA Energy Efficiency Series, Working Paper, 2011.

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/eeb054706cc0fdec4a252ed031c1061a.png) 
Fig. 1 Effect of Si and Al addition on the soft magnetic properties of Fe-18Co alloy

Effect of Si/Al addition on magnetic properties of Fe Co alloy

Motor cores usually operate at high temperatures, and the temperature affects their magnetic properties. It has been shown that the iron loss of 3.5% silicon steel decreases with the increase of temperature, and a model of iron loss considering the effect of temperature is proposed[1-2], but this model is not applicable to high silicon steel. It is reported that the iron loss of 6.5% silicon steel increases with the temperature[3]. Therefore, the study on the evolution of the temperature-dependent iron loss of silicon steel with different Si contents is particularly important, and there are few studies in this area. 
In the second part of this paper, the magnetic properties of silicon steels with different Si contents (2.5%, 3.5%, 4.5%, 5.5%, 6.5%) were tested at variable temperatures (-70°C-200°C) using a self-built multi-physical field coupling test system and non-standard ring sample test method, as shown in Fig 1.Some of the experimental results are shown in Fig 2, which reveal variation of iron loss law of silicon steel with different Si content under the effect of temperature, and explain the reason of this phenomenon from the internal microstructure of the material. The third part of this paper uses the above experimental data to reconstruct the loss model for a 6.5% silicon steel. The correlation analysis of temperature effects on eddy current losses and hysteresis losses of high silicon steel is carried out respectively, and the temperature-dependent loss coefficients are added to the corresponding mathematical model. The fourth part of this paper compares the experimental test data of high silicon steel loss, the calculated data of traditional loss model and the calculated data of this loss model to analyze their error accuracy, and finally verifies that for the loss calculation of high silicon steel, the proposed iron loss model is more accurate than the traditional calculation model.
Finally, this study will be of greater guidance for the design of subsequent high-silicon steel motors. 
**References:** [1] J. Q. Chen, D. Wang, and S. W. Cheng,“Modeling of temperature effects on magnetic property of non-oriented silicon steel lamination,” vol.51, no.11, Nov. 1, 2015. 
[2] N. Takahashi, M. Morishita, D. Miyagi, “Examination of magnetic properties of magnetic materials at high temperature using a ring specimen,”,vol. 46, no. 2, pp. 548–551, Feb.2010. 
[3] Ou, J, Liu, Y, Breining, P, Experimental Characterization and Feasibility Study on High Mechanical Strength Electrical Steels for High-Speed Motors Application. 57(1), 284-293. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/4a3c3dd75fd7f7fe652874b192df3647.png) 
Fig.1 Multiphysics coupled magnetic performance testing system and test sample 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/49da328d874c89be6f3d9286ed504723.png) 
Fig.2 (left) Iron loss curves at different temperatures. (right) Variation of iron loss with temperature

Study on the Loss Characteristics of Silicon Steel with Different Si Content Considering the Effect of Temperature

Studying the magnetic properties of the Grain-Oriented(GO) electrical steel under different stresses in a wide frequency range is of great significance for improving the energy conversion efficiency of the motors or transformers. Residual bending stress can cause deterioration of the magnetic properties of the motor and lead to an increase in core losses[1]. However, only the effect of bending stress on the magnetic properties of GO electrical steel sheets at 50 Hz has been studied so far, and the magnetic properties at higher frequencies magnetization under bending stress is still unclear[2]. Aiming at this problem, the magnetic properties of GO electrical steel sheet under different bending stress up to 1kHz is investigated by developing a measuring system under different curvature loading mechanisms. 
II Method and Discussion 
For investigating the magnetic properties of the GO steel sheet under different bending stress, the single sheet specimen to be measured were bended into different radius of curvatures as shown in Fig.1. Because of the deterioration of the magnetic characteristics caused by the bend of the sample, it is very difficult to maintain the sinusoidal waveform for standardized testing in the measurement process. A robust digital control algorithm in the frequency domain with a normalized dual-loop control loops is proposed. Fig.2 shows the some measuring results of GO steel B27R090. It can be found that with the increase of bending stress, the loss increases significantly and the higher the frequency, the greater the influence of bending stress is found. 
III Conclusion 
The magnetic properties of electrical steel under different bending stress over a wide frequency range are measured by the proposed measuring system with a normalized frequency domain dual-loop feedback control algorithm in this paper. Obtained results show that the bending stress of electrical steel sheet has a great influence on the iron loss, and the influence becomes more obvious with the increase of frequency. 
**References:** [1] T. Wang et al . Fabrication and Experimental Analysis of an Axially Laminated Flux-Switching Permanent-Magnet Machine [J]. IEEE Transactions on Industrial Electronics, vol. 64, no. 2, pp. 1081-1091, Feb. 2017. 
[2] H. Hagihara, Y. Takahashi, K. Fujiwara, Y. Ishihara and T. Masuda. Magnetic Properties Evaluation of Grain-Oriented Electrical Steel Sheets Under Bending Stress [J]. IEEE Transactions on Magnetics, vol. 50, no. 4, pp. 1-4, April 2014, Art no. 2002104. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/0103dfa4eae026846d34cfe7749fc6c8.png) 
Fig.1. Magnetic properties measurement system for electrical steel under bending stress and dual-loop control algorithm used. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/4520a27cc123ca183b85e04bcbdb9689.png) 
Fig.2. Measurement results of electrical steel at different bending stresses.

Measurement of magnetic properties of grain oriented electrical steel under bending stress in a wide frequency range

Accurate calculation of hysteresis properties of magnetic materials is of great significance for the optimal design of electromagnetic devices. At the state of the art, the J-A model is widely used in the FEM procedures as it is easy to implement. However, the existing J-A models relying on the parameters identified by the static limiting hysteresis loops can only ensure the accurate calculation of grain-oriented (GO) silicon steel sheets at high magnetic densities, which have relatively poor calculation accuracy at low magnetic densities[1]. Aiming at this problem, this paper proposes an improved J-A model, which can accurately and quickly calculate the global hysteresis loops of GO silicon steel sheets with only a small amount of data. 
II Method and Discussion 
As shown in Fig. 1, an improved anisotropic J-A model suitable for GO silicon steel sheets is proposed introducing the some variable parameters. To solve the problem of low calculation accuracy when the magnetized state of the material is far from saturation, a damping factor R is introduced to correct the irreversible changing susceptibility of the J-A model. Meanwhile, the pinning coefficient k and domain flexing coefficient c of the J-A model are assumed that should be changed with the magnetic flux density B. It can be seen from Fig.2 (a, b, c) that the parameters k, c, and R have a good functioning relationship with the magnetic flux density B, so the parameters under the remaining magnetic flux densities can be quickly obtained. The velocity-controlled particle swarm (VCPSO) algorithm is used to identify various parameters[2]. The calculation results are shown in Fig 2 (d), which are in good agreement with the experimental data. 
III Conclusion 
This paper presents an improved anisotropic J-A model by introducing a damping factor R and considering the parameter R, k and c are as a function of magnetic flux densities. Obtained results show that the proposed model can accurately and quickly simulate the global hysteresis characteristic of GO silicon steel sheets. 
**References:** [1] Podbereznaya I, Pavlenko A . Accounting for dynamic losses in the Jiles-Atherton model of magnetic hysteresis - ScienceDirect[J]. Journal of Magnetism and Magnetic Materials, 2020, 513. 
[2] Chen L , Yi Q , Tong B , et al. Parameter identification of Preisach model based on velocity-controlled particle swarm optimization method[J]. AIP Advances, 2021, 11(1):015022. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/c6902e5c2ddc186d07329fc54d27d712.png) 
Fig.1. Improved J-A Model Calculation Process 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/652f687d4e2df788009c47ea05d6c3b6.png) 
Fig.2. (a) Parameter k=f(B). (b) Parameter c=f(B). (c) Parameter R=f(B). (d) The simulation curve is compared with the measured data.

Accurate calculation of global hysteresis properties of grain oriented silicon steel based on an improved J

Axial flux motors for aviation systems operate at high altitudes, and the initial operating temperature of the motor is low, but due to the thin air, the motor temperature rise is high and the stator material temperature variation range is large[1], especially the segmented stator is close to the motor winding coil, and the thermal stress has a non-negligible effect on its material[2]. The segmented stator laminated magnetic energy model has been extensively studied in past researches, and no research has been proposed to consider the magnetic energy model of the laminated structure under the thermal stress of the material.
When the temperature changes, the segmented stator is not completely free to expand and contract due to the external constraints and the mutual constraints between the internal parts, thus generating thermal stresses [3]. Previous studies have shown that the temperature itself affects the magnetic properties of the material. In this paper, we intend to analyze the magnetic properties of the material by means of a coupled material multiphysics field testbed, and to divide the temperature-induced effects into the effects of temperature on the inherent properties of the material itself and the effects of thermal stresses induced by temperature changes on grain-oriented silicon steel, and to separate them equivalently. In this paper, a comparative analysis of the stator with different thicknesses of grain-oriented silicon steel is carried out, and the deformation of different stator materials under thermal stress is calculated by finite elements. Finally, the thermal stress effect percentage is tested experimentally. It is found that the use of thinner oriented silicon steel material will greatly reduce the effect of thermal stress on its magnetic properties. 
**References:** [1] Paredes J A, Saito C, Abarca M, et al. Study of effects of high-altitude environments on multicopter and fixed-wing UAVs' energy consumption and flight time[C]//2017 13th IEEE Conference on Automation Science and Engineering (CASE). IEEE, 2017: 1645-1650. 
[2] Wu Y, Ming T, Li X, et al. Numerical simulations on the temperature gradient and thermal stress of a thermoelectric power generator[J]. Energy conversion and management, 2014, 88: 915-927. 
[3] Yong L, Liang W, Qian W, et al. Calculation of deformation and material stress of a rotary voice coil motor used in aerospace[J]. Journal of Computational and Theoretical Nanoscience, 2015, 12(11): 4499-4505. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/ad12fa7af598e8be47600947804b2b3b.png) 
Fig. 1 Multi-physics field testing of two materials 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/ef7ca7afbe17d67f3195dd0e775c393b.png) 
Fig. 2 Simulation and physical model

Analysis of the Stator Magnetic Properties of an Aerospace Axial Flux Motor Considering the Thermal Stress of Material Lamination

Anisotropic rare-earth thick-film magnets have various applications such as MEMS (Micro Electro Mechanical Systems) devices and miniaturized electronic devices[1][2]. We have already fabricated anisotropic rare-earth film magnets by the substrate heating[3][4]. In the substrate heating process, increasing the deposition time might cause the grain size of Nd-Fe-B to increase. Our approach to anisotropic Nd-Fe-B thick-film magnets is to make them by increasing laser beam power for high deposition rate. This contribution reports the effect of laser power on several properties of anisotropic Nd-Fe-B film magnets using PLD method.
A rotated Nd-Fe-B target was ablated using an Nd-YAG pulse laser. The laser beam power was set at 2-4 W. During deposition, a Ta substrate was heated by Joule heating utilizing electric current through the substrate. J-H loops were measured with a vibrating sample magnetometer (VSM). The perpendicular loops were corrected by using the demagnetization factor of 0.8.
Figure 1 shows J-H loops of the Nd-Fe-B films deposited at each laser power. The films had the easy direction of magnetization in the plane of the perpendicular. The residual magnetic polarization ratio is defined by Jrper / Jrin , where Jrper and Jrin are the residual magnetic polarization values out-of-plane and in-plane direction, respectively. Jrper / Jrin ratio suggests that the decreasing laser power puts the easy direction of magnetization out-of-plane of the film.
Figure 2 shows X-ray diffraction patterns of samples deposited by 2 W and 4 W. The peak intensities corresponding to the c-axis prepared by laser beam power at 2 W were stronger than those for 4 W. As the relative intensity ratio of (006) / (105) increase with the decreasing laser beam power {4 W : 0.8 , 2 W : 1.3} , the increase in intensity ratio is consistent with the increase in the Jrper / Jrin value. Although it was difficult to prepare anisotropy Nd-Fe-B films with high deposition rate, we found that the crystalline texture for the Nd-Fe-B film magnets depends on the laser power. 
**References:** [1] P. Mcguiness, D. Jezeršek, S. Kobe, J. Magn. Magn. Mater., vol. 305, no. 1, pp. 177–181 (2006). 
[2] R. Fujiwara, T. Shinshi, and M. Uehara, Int. J. Automot. Technol., vol. 7, no. 2, pp. 148–155 (2013). 
[3] M. Nakano, S. Tsutsumi, T. Yanai, J. Appl. Phys., vol. 105, Issue 7, pp. 07A739-07A742 (2009). 
[4] Y. Furukawa, H. Koga, T. Yanai , IEEE Magn. Lett. , vol. 8, #5502104 (2017). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/87aec14f2d60a6395741126fbc6a6b26.png) 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/d0816ccc64b47ccabc4f66100973bf80.png)

Effect of laser power on structural and magnetic properties of anisotropic Nd Fe

A lot of researchers have reported anisotropic (Nd or Pr) -Fe-B films prepared by a sputtering method [1]. In the experiment, the condition of annealing processes has been deeply investigated for obtaining excellent magnetic properties. We have demonstrated a miniaturized motor including PLD (Pulsed Laser Deposition)-fabricated isotropic (Nd or Pr) -Fe-B films with rare-earth rich composition compared to stoichiometric one [2]. Due to amorphous structure after the laser deposition, post-annealing is required to form the 2-14-1 phase to obtain isotropic hard magnetic films. Although a detailed investigation on the crystallization process is required to enhance isotropic magnetic properties, unfortunately there are not many reports on isotropic (Nd or Pr)-Fe-B films. In the study, we focused on the different phenomena through a post-annealing between isotropic rare-earth rich Nd-Fe-B and Pr-Fe-B films. 
Figure 1 shows coercivity of (Nd or Pr)-Fe-B films with rare earth content of 15.5 - 18.5 at. % as a function of annealing temperature in a resistance heating furnace. While the coercivity value of Nd-Fe-B films did not change up to 650 °C, the value of Pr-Fe-B films enhanced between 600 and 650 °C. Moreover, figure 2 shows the results of pulse (flash) annealing using an infrared furnace after the deposition of rare earth-rich (Nd or Pr)-Fe-B films. Although two films were annealed at the same annealing time of 1.7 s, the shoulder of a J-H loop (dotted line) for only a Pr-Fe-B film was open. X-ray diffraction patterns indicate that the 2-14-1 phase formed in the Pr-Fe-B film. In contrast, we observed that the Nd-Fe-B film had amorphous structure. Assuming that the crystallization temperatures of Pr2Fe14B and Nd2Fe14B phases are the same, the phenomenon is due to the difference in diffusion transfer of each rare earth atom during the annealing process. We consider the correlation between the diffusion transfer and the melting points (Nd: 1024 °C, Pr: 930 °C) of each element. 
**References:** [1] N. M. Dempsey et.al., Appl. Phys. Lett. Vol. A90, 092509(2007). 
[2] 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/6cbc7197474cb0bd8c9b461d9f419d95.png) 
Fig. 1 Coercivity values of isotropic Pr-Fe-B and Nd-Fe-B films as a function of annealing temperature. (resistance heating furnace) 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/4d10335af1c50deecf36584a7dfa99b1.png) 
Fig. 2 J-H loops of Pr-Fe-B(dotted line) and Nd-Fe-B(solid line) films annealed at 1.7 s. (infrared furnace)

Investigation on crystallization process in isotropic rare earth rich (Nd or Pr)

Although Nd-Fe-B thick-films with the thickness above 10 microns have been prepared by a sputtering and a PLD (Pulsed Laser Deposition) to develop the miniaturization of devices including a magnet [1][2], it is generally said that the sputtering is not suitable for a thick-film process due to the limitation of deposition rate and the PLD has difficulty in achieving the both of large deposition area together with high deposition rate. In the case of PLD-made Nd-Fe-B films, the area has been fixed at 5 mm square. Recently, we proposed a vacuum arc deposition with a rotational substrate system to obtain an isotropic Nd-Fe-B film magnet with a 20 mm square under a deposition rate above 10 μm/h. Furthermore, compositional and thickness distribution could be reduced to ±0.4 % and ±16 %, respectively. We, however, found that the squareness of a J-H loop and (BH)max drastically deteriorated at the edge of the sample. This contribution reports improvement of the deterioration by taking advantage of Nb additive to achieve target values of magnetic properties (Hcb > 420 kA/m, Br > 0.78 T, (BH)max> 62 kJ/m3) applied to a miniaturized device. 
Figure 1 shows the relationship between coercivity (Hcb) and squareness of post-annealed Nd-Fe-B films after the vacuum arc deposition. Each symbol shows the properties of 5 mm square films cut from different area in a 20 mm square (Black circle, Black triangle: within 10 mm square from the center) and the edges (White circle, White triangle : outside of Black circle,Black triangle ). Usage of Nb additive enabled us to improve the squareness and suppress the dependence of deposition position. Moreover, Scherr’s equation using X-ray diffraction patterns reveled that the distribution of grain size due to the different deposition positions could be reduced by using Nb additive. It was also clarified that the target values except Hcb could be achieved. 
**References:** [1] N. M. Dempsey et.al., Appl. Phys. Lett. Vol. A90, 092509(2007). 
[2] M. Nakano et al., IEEE Trans. Mag. vol.56, 7516303(2020). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/80c246b9f4b24fbd23bdeda7243fabb9.png) 
Fig. 1 Relationship between coercivity and squareness of post-annealed films deposited on different positions.

Preparation of Nd Fe

Sputtering-made Nd-Fe-B films with the thickness of 20 microns on Si substrates are expected to apply magnetic materials to MEMS (Micro Electro Mechanical Systems) as future devices of a miniaturized sensor and actuator [1]. On the other hand, we have fabricated isotropic Nd-Fe-B thick-film magnets thicker than 100 microns on Si substrates by a PLD (Pulsed Laser Deposition) method [2]. In addition, micro-magnetization of the thick-films could be achieved by taking advantage of a glass buffer layer [3]. Investigation on an optimum condition to enhance magnetic properties of Nd-Fe-B/glass two-layered films, however, has not been completed, since there are many parameters of the fabrication process such as Nd contents, annealing conditions and thicknesses ratio of each film. 
In the study, annealing time in a pulse-annealing process after the deposition was optimized at 4.0 s through systematic investigation under Nd contents range from 14 to 16 at.%. Moreover, effect of the thickness ratio of a glass film and an isotropic Nd-Fe-B film on magnetic properties was examined. Figure 1 shows coercivity as a function of the ratio. Here, each thickness varied from 15 to 60 microns for Nd-Fe-B films and 12 to 114 microns for glass films, respectively. It was found that the ratio less than 2 enabled us to increase coercivity up to 500 kA/m. The detail mechanism of the phenomenon is under investigation. In addition, J-H loops of Nd-Fe-B/glass two-layered films on Si substrates were compared as seen in Fig. 2. The red loop and dotted loop are corresponding to an obtained film showed in Fig. 1 and a micro-magnetized film reported in the reference [3], respectively. Enhancement of (BH)max could be achieved through the above-mentioned optimization. 
**References:** [1] R Fujiwara et al., Int. J. Autom. Technol. Vol. 7, 148(2013). 
[2] M. Nakano et al., IEEE Trans. Magn. Vol. 51, 2102604 (2015). 
[3] D. Han et al., IEEE Magn. Letters, Vol. 11, 8103804 (2020). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/9ff8537e8ba4867e1ebb815672550b4a.png) 
Fig.1 Coercivity of samples as a function of thickness ratio 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/b84d5cff5ac42e0186f2688cd053abb8.png) 
Fig.2 Comparison of J-H loops of two Nd-Fe-B-glass samples

Improvement in magnetic properties of Nd Fe

Sm(Fe0.8Co0.2)12 thin films with the ThMn12 type crystal structure are expected as a new high-performance permanent magnet material because they possess excellent magnetic properties such as high saturation magnetization µ0Ms of 1.78 T, anisotropy field µ0HA of 12 T and Curie temperature TC of 879 K [1]. Recently, it has been clarified that a coercive force µ0Hc as high as 1.2 T can be successfully obtained in the Sm(Fe-Co) thin films with B addition. It is considered that this is mainly due to the formation of RFe12 grains with columnar structure separated by the B-rich amorphous grain boundary phase [2]. In addition, µ0Hc was further increased by the diffusion of Si into the grain boundary phase in the Sm(Fe-Co)-B thin films. Then, it is predicted that µ0Hc will be further increased by reducing the soft magnetic phase existing at the vicinity of the initial interface between V under layer and Sm(Fe-Co)-B main layer [3]. In this study, a Sm seed layer was inserted between the V under layer and the Sm(Fe-Co) layer to suppress the initial growth of soft magnetic phase such as α-Fe and α-(Fe-Co), and the crystal structure and magnetic properties were investigated in detail. The samples were prepared by using the ultra-high vacuum magnetron sputtering system. First of all, a V buffer layer of 20 nm was deposited onto the MgO (100) single crystal substrate at substrate temperature Ts of 673 K. Then, the thickness tSm of the Sm seed layer was changed from 0 to 5 nm and while that of Sm(Fe-Co)-B layer was fixed at 100 nm. Finally, a V cover layer of 10 nm was deposited. The B composition was changed up to 5 at.%. It was confirmed that the introduction of the Sm seed layer into Sm(Fe-Co) layer clearly decreases the intensity of the peaks obtained from α-(Fe-Co) and increases the intensity of the (002) and (004) peaks in the RFe12 phase. In addition, improvement of remanent magnetization ratio while maintaining µ0Hc above 1.0 T was confirmed. It was thought that the Sm seed layer plays an important role to suppress the formation of α-(Fe-Co) phase and to improve the orientation of the 1:12 phase. The detailed results will be discussed at the conference. 
**References:** [1] Y. Hirayama, Y. K. Takahashi, S. Hirosawa and K. Hono, Scr. Mater., 138 (2017) 62-65. 
[2] Sepehri-Amin, Y. Tamazawa, M. Kambayashi, G. Saito, Y. K. Takahashi, D. Ogawa, T. Ohkubo, S. Hirosawa, M. Doi, T. Shima, K. Hono, Scr. Mater., 194 (2020) 337-342. 
[3] A. Boyachkin, H. Sepehri-Amin, M. Kambayashi, Y. Mori, T. Ohkubo, Y. K. Takahashi, T. Shima, K. Hono, Acta. Mater., 227 (2022) 117716.

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